Method, and related apparatus for recovering called service of terminal

ABSTRACT

Embodiments of the present invention disclose a method, a related apparatus, and a system for recovering a called service of a terminal. The method includes: when a called request of a user terminal is received, querying an initial proxy-call session control function (P-CSCF) entity with which the user terminal currently registers; if it is detected that the initial P-CSCF is faulty, selecting an available P-CSCF and sending, to the available P-CSCF, a notification message that carries a redundancy identifier, where the redundancy identifier is used to instruct the available P-CSCF to trigger the user terminal to re-register with the P-CSCF; and when a registration complete message sent by the P-CSCF with which the user terminal re-registers is received, delivering the called request to the re-registered P-CSCF to bear a called service of the user terminal.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of International Patent ApplicationNo. PCT/CN2014/081582, filed on Jul. 3, 2014, which claims priority toChinese Patent Application No. 201310342761.0, filed on Aug. 7, 2013,both of which are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

Embodiments of the present invention relates to the field ofcommunications technologies, and in particular, to a method, a relatedapparatus, and a system for recovering a called service of a terminal.

BACKGROUND

A CSCF (Call Session Control Function) is a functional entity in aninternet protocol (IP) multimedia subsystem (IMS), and is mainlyresponsible for processing signaling control in a multimedia callsession process. The CSCF may be classified into a P-CSCF (proxy CSCF),an I-CSCF (interrogating CSCF), and an S-CSCF (serving CSCF).

In a service control process, if the P-CSCF is faulty, and if a userterminal that registers with the P-CSCF is used as a called party, andthe S-CSCF finds the P-SCCF fault when managing a called service, a userof the terminal cannot be contacted by using the P-CSCF, which causes aservice failure.

In the prior art, two P-CSCFs form primary and secondary P-CSCFs, andwhen one P-CSCF is faulty, a service may be taken over by the secondaryP-CSCF. A same IP address IP1 is configured for a P-CSCF1 and a P-CSCF2.Generally, the P-CSCF1 advertises a route of the P-CSCF1 to the outside,but the P-CSCF2 does not advertise an address of the P-CSCF2. First, theuser terminal sends a registration request to the IP1 and registers withthe primary P-CSCF1, and the P-CSCF1 backs up user registrationinformation in the secondary P-CSCF2. When the P-CSCF1 is faulty, theP-CSCF2 can sense, by means of heartbeats, that the P-CSCF1 is faulty.In this case, the P-CSCF2 advertises a route of the P-CSCF2 to theoutside, and then a service of the terminal is routed to the P-CSCF2 forprocessing. Because user information has been backed up during previousregistration, the new P-CSCF2 can correctly process a request of theuser.

In the prior art, main disadvantages of a data backup solution betweenprimary and secondary network elements include: heartbeat detection isperformed between a primary network element and a secondary networkelement, which is prone to a dual-host fault, causing a problem thatneither the primary network element nor the secondary network elementcan perform a service. In addition, the primary network element and thesecondary network element present a same IP to the outside, whichrequires support from a near-end router, where processing is relativelycomplex.

SUMMARY

A technical problem to be resolved in embodiments of the presentinvention is to provide a method, a related apparatus, and a system forrecovering a called service of a terminal, which can quickly recover acalled service of a user terminal when a P-CSCF is faulty.

According to a first aspect, the embodiments of the present inventionprovide a method for recovering a called service of a terminal,including:

when a called request of a user terminal is received, querying aninitial proxy-call session control function (P-CSCF) entity with whichthe user terminal currently registers; and

if it is detected that the initial P-CSCF is faulty, selecting anavailable P-CSCF and sending a notification message to the availableP-CSCF to trigger the user terminal to re-register with the P-CSCF,where

the available P-CSCF triggers, by using a policy and charging rulesfunction PCRF entity, the user terminal to re-register with the P-CSCF.

In a first possible implementation manner of the first aspect, thesending a notification message to the available P-CSCF to trigger theuser terminal to re-register with the P-CSCF includes:

sending, to the available P-CSCF, a notification message that carries aredundancy identifier, where the redundancy identifier is used toinstruct the available P-SCCF to trigger the user terminal tore-register with the P-CSCF.

In a second possible implementation manner of the first aspect, thesending a notification message to the available P-CSCF to trigger theuser terminal to re-register with the P-CSCF includes:

sending the called request of the user terminal to the available P-CSCF;and

when the available P-CSCF determines that no registration data of acalled user is stored, triggering the user terminal to re-initiate IMSregistration. According to a second aspect, the embodiments of thepresent invention further provide another method for recovering a calledservice of a terminal, including: receiving a notification message thatis sent by a serving-call session control function (S-CSCF) entity andcarries a user name;

generating, if it is found, by means of parsing, that the notificationmessage further includes a redundancy identifier, a reselection requestthat carries a P-CSCF re-select flag and the user name; and

sending the reselection request to a policy and charging rules function(PCRF) entity that manages a user terminal indicated by the user name,so that the PCRF instructs, according to the P-CSCF re-select flag, theuser terminal indicated by the user name to reselect a P-CSCF to bear acalled service of the user terminal, where

the notification message that carries the redundancy identifier isgenerated by the S-CSCF when a P-CSCF with which the user terminalcorresponding to a received called request registers is faulty, and theredundancy identifier is used to instruct to trigger the user terminalto re-register with a P-CSCF.

With reference to the second aspect, in a first possible implementationmanner, the sending the reselection request to a PCRF entity thatmanages a user terminal indicated by the user name includes:

sending the reselection request to a Diameter routing agent (DRA), sothat the DRA sends, according to the user name in the reselectionrequest, the reselection request to the PCRF that manages the userterminal indicated by the user name.

With reference to the second aspect or the first possible implementationmanner of the second aspect, in a second possible implementation manner,before the generating, if it is found, by means of parsing, that thenotification message further includes a redundancy identifier, areselection request that carries a P-CSCF re-select flag and the username, the method further includes:

determining whether the user terminal indicated by the user nameregisters with a local end; and

if the user terminal does not register with the local end, performingthe generating, if it is found, by means of parsing, that thenotification message further includes a redundancy identifier, areselection request that carries a P-CSCF re-select flag and the username.

With reference to the second aspect, or the first possibleimplementation manner of the second aspect, or the second possibleimplementation manner of the second aspect, in a third possibleimplementation manner, the method further includes:

when a registration request of the user terminal is received, sending aregistration complete message to an S-CSCF to which the user terminalbelongs, to complete registration of the user terminal.

According to a third aspect, the embodiments of the present inventionfurther provide still another method for recovering a called service ofa terminal, including:

generating a registration triggering request when a reselection requestthat is sent by a P-CSCF and carries a P-CSCF re-select flag and a username is received; and

sending the generated registration triggering request to a gatewayconnected to a user terminal indicated by the user name, so that thegateway triggers the user terminal indicated by the user name tore-register with a P-CSCF to bear a called service of the user terminal,where

the reselection request is generated by the P-CSCF according to anotification message that is sent by an S-CSCF and carries the user nameand a redundancy identifier, where the redundancy identifier is used toinstruct to trigger the user terminal indicated by the user name tore-register with the P-CSCF.

With reference to the third aspect, in a first possible implementationmanner, the generating a registration triggering request when areselection request that is sent by a P-CSCF and carries a P-CSCFre-select flag and a user name is received includes:

when the reselection request that is sent by the P-CSCF and carries theP-CSCF re-select flag and the user name is received, generating aregistration triggering request that carries a session release message,where

the session release message is used to instruct the gateway connected tothe user terminal indicated by the user name to request a mobilitymanagement entity (MME) to delete a user bearer of a user terminal.

With reference to the third aspect, in a second possible implementationmanner, the generating a registration triggering request when areselection request that is sent by a P-CSCF and carries a P-CSCFre-select flag and a user name is received includes:

when the reselection request that is sent by the P-CSCF and carries theP-CSCF re-select flag and the user name is received, generating aregistration triggering request that carries update P-CSCF addressinformation, where

the update P-CSCF address information is used to instruct the gatewayconnected to the user terminal indicated by the user name to generate alist of available P-CSCF addresses and send the list of the availableP-CSCF addresses to the user terminal indicated by the user name.

According to a fourth aspect, the embodiments of the present inventionfurther provide yet another method for recovering a called service of aterminal, including:

when a registration triggering request that is sent by a policy andcharging rules function PCRF entity and carries a user name is received,triggering a user terminal indicated by the user name to re-registerwith a P-CSCF to bear a called service of the user terminal, where

the registration triggering request is generated when the PCRF receivesa reselection request that is sent by a P-CSCF and carries a P-CSCFre-select flag and the user name, and the reselection request isgenerated by the P-CSCF according to a notification message that is sentby an S-CSCF and carries the user name and a redundancy identifier,where the redundancy identifier is used to instruct to trigger the userterminal indicated by the user name to re-register with the P-CSCF.

With reference to the fourth aspect, in a first possible implementationmanner, the triggering a user terminal indicated by the user name tore-register with a P-CSCF includes:

when the registration triggering request carries a session releasemessage, sending, to an MME, a release request that carries the username, so that the MME deletes a user bearer of the user terminalindicated by the user name; or

when the registration triggering request carries update P-CSCF addressinformation, acquiring a list of available P-CSCF addresses and sendingthe list of the available P-CSCF addresses to the user terminalindicated by the user name, so that the user terminal selects a P-CSCFfrom the list of the available P-CSCF addresses and registers with theselected P-CSCF.

According to a fifth aspect, the embodiments of the present inventionfurther provide yet another method for recovering a called service of aterminal, including:

when an access failure is detected, initiating a registration requestfor registering with a P-CSCF, so that a re-registered P-CSCF bears acalled service when an initial P-CSCF is faulty; and

when a list of available P-CSCF addresses that is sent by a gateway isreceived, selecting a P-CSCF from the list of the available P-CSCFaddresses and registering with the selected P-CSCF, so that there-registered P-CSCF bears the called service when the initial P-CSCF isfaulty.

With reference to the fifth aspect, in a first possible implementationmanner, the selecting a P-CSCF from the list of the available P-CSCFaddresses and registering with the selected P-CSCF, when a list ofavailable P-CSCF addresses that is sent by a gateway is receivedincludes:

when the list of the available P-CSCF addresses that is sent by thegateway is received, determining whether the list of the availableP-CSCF addresses includes a host name of the initial P-CSCF with which auser terminal currently registers; and

if the list of the available P-CSCF addresses does not include the hostname of the initial P-CSCF, selecting the P-CSCF from the list of theavailable P-CSCF addresses and registering with the selected P-CSCF.

According to a sixth aspect, the embodiments of the present inventionprovide an apparatus for recovering a called service of a terminal,including:

a querying module, configured to: when a called request of a userterminal is received, query an initial P-CSCF entity with which the userterminal currently registers; and

a processing module, configured to: if it is detected that the initialP-CSCF is faulty, select an available P-CSCF and send a notificationmessage to the available P-CSCF to trigger the user terminal tore-register with the P-CSCF, where

the available P-CSCF triggers, by using a PCRF entity, the user terminalto re-register with the P-CSCF.

With reference to the sixth aspect, in a first possible implementationmanner, the processing module is specifically configured to: afterselecting the available P-CSCF, send, to the available P-CSCF, thenotification message that carries a redundancy identifier, where theredundancy identifier is used to instruct the available P-SCCF totrigger the user terminal to re-register with the P-CSCF.

With reference to the first possible implementation manner of the sixthaspect, in a second possible implementation manner, the processingmodule is specifically configured to: after selecting the availableP-CSCF, send the called request of the user terminal to the availableP-CSCF, so as to trigger, when the available P-CSCF determines that noregistration data of a called user is stored, the user terminal tore-initiate IMS registration.

According to a seventh aspect, the embodiments of the present inventionfurther provide another apparatus for recovering a called service of aterminal, including:

a receiving module, configured to receive a notification message that issent by a S-CSCF entity and carries a user name;

a processing module, configured to generate, if it is found, by means ofparsing, that the notification message further includes a redundancyidentifier, a reselection request that carries a P-CSCF re-select flagand the user name; and

a sending module, configured to send the reselection request to a PCRFentity that manages a user terminal indicated by the user name, so thatthe PCRF instructs, according to the P-CSCF re-select flag, the userterminal indicated by the user name to reselect a P-CSCF to bear acalled service of the user terminal, where

the notification message that carries the redundancy identifier isgenerated by the S-CSCF when a P-CSCF with which the user terminalcorresponding to a received called request registers is faulty, and theredundancy identifier is used to instruct to trigger the user terminalto re-register with a P-CSCF.

With reference to the seventh aspect, in a first possible implementationmanner, the sending module is specifically configured to send thereselection request to a DRA, so that the DRA sends, according to theuser name in the reselection request, the reselection request to thePCRF that manages the user terminal indicated by the user name.

With reference to the seventh aspect or the first possibleimplementation manner of the seventh aspect, in a second possibleimplementation manner, the apparatus further includes:

a determining module, configured to: determine whether the user terminalindicated by the user name registers with a local end, and when a resultof the determining is that the user terminal does not register with thelocal end, instruct the processing module to perform the generating, ifit is found, by means of parsing, that the notification message furtherincludes a redundancy identifier, a reselection request that carries aP-CSCF re-select flag and the user name.

With reference to the seventh aspect, or the first possibleimplementation manner of the seventh aspect, or the second possibleimplementation manner of the seventh aspect, in a third possibleimplementation manner, the apparatus further includes:

a registering module, configured to: when a registration request of theuser terminal is received, send a registration complete message to anS-CSCF to which the user terminal belongs, to complete registration ofthe user terminal.

According to an eighth aspect, the embodiments of the present inventionfurther provide still another apparatus for recovering a called serviceof a terminal, including:

a generating module, configured to generate a registration triggeringrequest when a reselection request that is sent by a P-CSCF and carriesa P-CSCF re-select flag and a user name is received; and

a sending module, configured to send the generated registrationtriggering request to a gateway connected to a user terminal indicatedby the user name, so that the gateway triggers the user terminalindicated by the user name to re-register with a P-CSCF to bear a calledservice of the user terminal, where

the reselection request is generated by the P-CSCF according to anotification message that is sent by an S-CSCF and carries the user nameand a redundancy identifier, where the redundancy identifier is used toinstruct to trigger the user terminal indicated by the user name tore-register with the P-CSCF.

With reference to the eighth aspect, in a first possible implementationmanner, the generating module is specifically configured to: when thereselection request that is sent by the P-CSCF and carries the P-CSCFre-select flag and the user name is received, generate a registrationtriggering request that carries a session release message, where

the session release message is used to instruct the gateway connected tothe user terminal indicated by the user name to request an MME to deletea user bearer of a user terminal.

With reference to the eighth aspect, in a second possible implementationmanner, the generating module is specifically configured to: when thereselection request that is sent by the P-CSCF and carries the P-CSCFre-select flag and the user name is received, generate a registrationtriggering request that carries update P-CSCF address information, where

the update P-CSCF address information is used to instruct the gatewayconnected to the user terminal indicated by the user name to generate alist of available P-CSCF addresses and send the list of the availableP-CSCF addresses to the user terminal indicated by the user name.

According to a ninth aspect, the embodiments of the present inventionfurther provide yet another apparatus for recovering a called service ofa terminal, including:

a receiving unit, configured to receive a registration triggeringrequest that is sent by a PCRF entity and carries a user name; and

a triggering module, configured to trigger a user terminal indicated bythe user name to re-register with a P-CSCF to bear a called service ofthe user terminal, where

the registration triggering request is generated when the PCRF receivesa reselection request that is sent by a P-CSCF and carries a P-CSCFre-select flag and the user name, and the reselection request isgenerated by the P-CSCF according to a notification message that is sentby an S-CSCF and carries the user name and a redundancy identifier,where the redundancy identifier is used to instruct to trigger the userterminal indicated by the user name to re-register with the P-CSCF.

With reference to the ninth aspect, in a first possible implementationmanner, the triggering module includes:

a first sending unit, configured to: when the registration triggeringrequest carries a session release message, send, to an MME, a releaserequest that carries the user name, so that the MME deletes a userbearer of the user terminal indicated by the user name; or

a second sending unit, configured to: when the registration triggeringrequest carries update P-CSCF address information, acquire a list ofavailable P-CSCF addresses and send the list of the available P-CSCFaddresses to the user terminal indicated by the user name, so that theuser terminal selects a P-CSCF from the list of the available P-CSCFaddresses and registers with the selected P-CSCF.

According to a tenth aspect, the embodiments of the present inventionfurther provide yet another apparatus for recovering a called service ofa terminal, including:

a registration initiating module, configured to: when an access failureis detected, initiate a registration request for registering with aP-CSCF, so that a re-registered P-CSCF bears a called service when aninitial P-CSCF is faulty; and

a registration selection module, configured to: when a list of availableP-CSCF addresses that is sent by a gateway is received, select a P-CSCFfrom the list of the available P-CSCF addresses and register with theselected P-CSCF, so that the re-registered P-CSCF bears the calledservice when the initial P-CSCF is faulty.

With reference to the tenth aspect, in a first possible implementationmanner, the registration selection module includes:

a determining unit, configured to: when the list of the available P-CSCFaddresses that is sent by the gateway is received, determine whether thelist of the available P-CSCF addresses includes a host name of theinitial P-CSCF with which a user terminal currently registers; and

a registration selecting unit, configured to: if the list of theavailable P-CSCF addresses does not include the host name of the initialP-CSCF, select the P-CSCF from the list of the available P-CSCFaddresses and register with the selected P-CSCF.

According to an eleventh aspect, the embodiments of the presentinvention further provide a system for recovering a called service of aterminal, including: a S-CSCF entity, at least two proxy-call sessioncontrol function P-CSCF entities, and a user terminal, where the atleast two P-CSCFs include a second P-CSCF and a first P-CSCF with whichthe user terminal currently registers; where

the S-CSCF is configured to: when a called request of the user terminalis received, query the first P-CSCF with which the user terminalcurrently registers; and if it is detected that the first P-CSCF isfaulty, select the second P-CSCF and send, to the second P-CSCF, anotification message that carries a redundancy identifier, where theredundancy identifier is used to instruct the available P-CSCF totrigger the user terminal to re-register with the P-CSCF;

the second P-CSCF is configured to trigger the user terminal tore-register with the P-CSCF; and

the S-CSCF is further configured to: when a registration completemessage sent by the P-CSCF with which the user terminal re-registers isreceived, deliver the called request to the re-registered P-CSCF to beara called service of the user terminal, where

the second P-CSCF specifically triggers, by using a policy and chargingrules function PCRF entity, the user terminal to re-register with theP-CSCF.

With reference to the eleventh aspect, in a first possibleimplementation manner, the system further includes a DNS server;

the S-CSCF is further configured to configure, on the DNS server, afirst identifier and a second identifier according to a host name of thefirst P-CSCF, where the first identifier includes an IP address of thefirst P-CSCF, and the second identifier includes an IP address of thesecond P-CSCF.

With reference to the eleventh aspect, or the first possibleimplementation manner of the eleventh aspect, in a second possibleimplementation manner, the system further includes a policy and chargingrules function PCRF entity;

the second P-CSCF is specifically configured to: generate, according tothe notification message that is sent by the S-CSCF and carries a username and the redundancy identifier, a reselection request that carries aP-CSCF re-select flag and the user name, and send the reselectionrequest to the PCRF; and

the PCRF is configured to instruct, according to the P-CSCF re-selectflag, the user terminal indicated by the user name to reselect a P-CSCFto bear the called service of the user terminal.

With reference to the second possible implementation manner of theeleventh aspect, in a third possible implementation manner, the systemfurther includes a DRA;

the DRA is configured to: receive the reselection request sent by thesecond P-CSCF, and send the reselection request to the PCRF.

With reference to the second possible implementation manner of theeleventh aspect, or the third possible implementation manner of theeleventh aspect, in a fourth possible implementation manner, the systemfurther includes a gateway connected to the user terminal;

the PCRF is specifically configured to: generate a registrationtriggering request when the reselection request that is sent by theP-CSCF and carries the P-CSCF re-select flag and the user name isreceived, and send the registration triggering request to the gateway;and

the gateway is configured to trigger, according to the registrationtriggering request, the user terminal indicated by the user name tore-register with the P-CSCF to bear the called service of the userterminal.

With reference to the fourth possible implementation manner of theeleventh aspect, in a fifth possible implementation manner,

the gateway is specifically configured to: when the registrationtriggering request carries a session release message, send, to an MME, arelease request that carries the user name, so that the MME deletes auser bearer of the user terminal indicated by the user name; or

when the registration triggering request carries update P-CSCF addressinformation, acquire a list of available P-CSCF addresses and send thelist of the available P-CSCF addresses to the user terminal indicated bythe user name, so that the user terminal selects a P-CSCF from the listof the available P-CSCF addresses and registers with the selectedP-CSCF.

With reference to the fifth possible implementation manner of theeleventh aspect, in a sixth possible implementation manner,

the user terminal is further configured to: when an access failure isdetected, initiate a registration request for registering with a P-CSCF,so that a re-registered P-CSCF bears the called service when the initialP-CSCF is faulty; or when the list of the available P-CSCF addressesthat is sent by the gateway is received, select a P-CSCF from the listof the available P-CSCF addresses and register with the selected P-CSCF,so that the re-registered P-CSCF bears the called service when theinitial P-CSCF is faulty.

According to a twelfth aspect, the embodiments of the present inventionprovide a method for recovering a called service of a terminal,including:

receiving a called request of a user terminal;

determining that no registration data of a called user is stored; and

sending, to a policy and charging rules function (PCRF) entity thatmanages the user terminal, a request for triggering the user terminal tore-initiate IMS registration.

According to a thirteenth aspect, the embodiments of the presentinvention provide an apparatus for recovering a called service of aterminal, including:

a receiving module, configured to receive a called request of a userterminal;

a processing module, configured to: when the receiving module receivesthe called request, determine that no registration data of a called useris stored; and

a sending module, configured to: after the processing module determinesthat no registration data of the called user is stored, send, to a PCRFthat manages the user terminal, a request for triggering the userterminal to re-initiate IMS registration.

In the embodiments of the present invention, after a called request isreceived, if it is detected that a P-CSCF with which a user terminalcorresponding to the called request currently registers is faulty, acorresponding message that carries a redundancy identifier is generatedto finally trigger the terminal to re-register with a P-CSCF, and acalled service of the user terminal is borne in the re-registeredP-CSCF, which avoids problems in the prior art that a dual-host fault iscaused because heartbeat detection needs to be performed between aprimary network element and a secondary network element and processingis complex because a same IP needs to be presented to the outside. Inaddition, fault recovery can be quickly completed in an existing networkarchitecture.

BRIEF DESCRIPTION OF DRAWINGS

To describe the technical solutions in the embodiments of the presentinvention more clearly, the following briefly introduces theaccompanying drawings required for describing the embodiments or theprior art. Apparently, the accompanying drawings in the followingdescription show merely some embodiments of the present invention, and aperson of ordinary skill in the art may still derive other drawings fromthese accompanying drawings without creative efforts.

FIG. 1 is a schematic flowchart of Embodiment 1 of a method forrecovering a called service of a terminal according to the presentinvention;

FIG. 2A is a schematic flowchart of Embodiment 2 of a method forrecovering a called service of a terminal according to the presentinvention;

FIG. 2B is a schematic flowchart of a method for recovering a calledservice of a terminal according to an embodiment of the presentinvention;

FIG. 3 is a schematic flowchart of Embodiment 3 of a method forrecovering a called service of a terminal according to the presentinvention;

FIG. 4 is a schematic flowchart of Embodiment 4 of a method forrecovering a called service of a terminal according to the presentinvention;

FIG. 5 is a schematic flowchart of Embodiment 5 of a method forrecovering a called service of a terminal according to the presentinvention;

FIG. 6 is a schematic flowchart of Embodiment 6 of a method forrecovering a called service of a terminal according to the presentinvention;

FIG. 7 is a schematic flowchart of Embodiment 7 of a method forrecovering a called service of a terminal according to the presentinvention;

FIG. 8 is a schematic flowchart of a method for recovering a calledservice of a terminal according to an embodiment of the presentinvention;

FIG. 9 is a schematic flowchart of a method for recovering a calledservice of a terminal according to an embodiment of the presentinvention;

FIG. 10 is a schematic structural diagram of Embodiment 1 of anapparatus for recovering a called service of a terminal according to thepresent invention;

FIG. 11A is a schematic structural diagram of Embodiment 2 of anapparatus for recovering a called service of a terminal according to thepresent invention;

FIG. 11B is a schematic structural diagram of an apparatus forrecovering a called service of a terminal according to an embodiment ofthe present invention;

FIG. 12 is a schematic structural diagram of Embodiment 3 of anapparatus for recovering a called service of a terminal according to thepresent invention;

FIG. 13 is a schematic structural diagram of Embodiment 4 of anapparatus for recovering a called service of a terminal according to thepresent invention;

FIG. 14 is a schematic structural diagram of Embodiment 5 of anapparatus for recovering a called service of a terminal according to thepresent invention;

FIG. 15 is a schematic structural diagram of a system for recovering acalled service of a terminal according to an embodiment of the presentinvention;

FIG. 16 is a schematic structural diagram of a network device accordingto an embodiment of the present invention;

FIG. 17A is a schematic structural diagram of another network deviceaccording to an embodiment of the present invention;

FIG. 17B is a schematic structural diagram of an apparatus forrecovering a called service of a terminal according to an embodiment ofthe present invention;

FIG. 18 is a schematic structural diagram of still another networkdevice according to an embodiment of the present invention;

FIG. 19 is a schematic structural diagram of still another networkdevice according to an embodiment of the present invention; and

FIG. 20 is a schematic structural diagram of user equipment according toan embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

The following clearly describes the technical solutions in theembodiments of the present invention with reference to the accompanyingdrawings in the embodiments of the present invention. Apparently, thedescribed embodiments are merely some but not all of the embodiments ofthe present invention. All other embodiments obtained by a person ofordinary skill in the art based on the embodiments of the presentinvention without creative efforts shall fall within the protectionscope of the present invention.

When a user performs a called service by using a user terminal, if aP-CSCF with which the user terminal currently registers is faulty, theuser terminal is triggered, by using another P-CSCF in a P-CSCF pool, tore-register with a new P-CSCF.

Referring to FIG. 1, FIG. 1 is a schematic flowchart of Embodiment 1 ofa method for recovering a called service of a terminal according to thepresent invention. The method in this embodiment of the presentinvention may be implemented in an S-CSCF or an IBCF (interconnectionborder control function). Specifically, the method in this embodiment ofthe present invention includes the following steps:

S101: When a called request of a user terminal is received, query aninitial proxy-call session control function P-CSCF entity with which theuser terminal currently registers.

After the user terminal registers with a P-CSCF, the P-CSCF sendscorresponding registration complete information to an S-CSCF, and theS-CSCF performs authentication and performs processing such asregistering a user name of the user terminal and a host name of theP-CSCF with which the user terminal registers. Therefore, according to auser name of the user terminal corresponding to the called request, theS-CSCF may query and determine the initial P-CSCF with which the userterminal currently registers. The user name of the user terminal is usedto identify the user terminal, and may be specifically an IP address, auser service permission, other user configuration information, and thelike of the user terminal.

S102: If it is detected that the initial P-CSCF is faulty, select anavailable P-CSCF and send a notification message to the available P-CSCFto trigger the user terminal to re-register with the P-CSCF.

The S-CSCF may perform heartbeat detection on each P-CSCF in a currentP-CSCF pool by using a heartbeat mechanism, and determine, according todata of the heartbeat detection or according to whether heartbeat datacan be normally received, whether the initial P-CSCF with which the userterminal currently registers is faulty. For example, it may bedetermined that the initial P-CSCF is faulty when a ping command (acommand used to check whether a network is good or a network connectionspeed) has no response or a detection message fails to be received orsent.

The notification message may be sent to the available P-CSCF in eitherof the following manners, so as to achieve an objective of triggeringthe user terminal to re-register with the P-CSCF:

Manner 1: Send, to the available P-CSCF, a notification message thatcarries a redundancy identifier, where the redundancy identifier is usedto instruct the available P-SCCF to trigger the user terminal tore-register with the P-CSCF;

Manner 2: Send the called request of the user terminal to the availableP-CSCF; and when the available P-CSCF determines that no registrationdata of a called user is stored, trigger the user terminal tore-initiate IMS registration. In Manner 2, the notification message isspecifically the called request. Optionally, when the available P-CSCFdetermines that the available P-CSCF does not store the registrationdata of the called user, the user terminal is triggered to re-initiatethe IMS registration. The called user is a user who uses the userterminal and is called.

It should be noted that the triggering the user terminal to re-registerwith the P-CSCF refers to triggering the user terminal to re-initiatethe IMS registration.

When it is detected that the initial P-CSCF is faulty, an availableP-CSCF is selected from the current P-CSCF pool. The available P-CSCFmay be a P-CSCF that is determined, by means of heartbeat detection orother manners, to be not faulty.

Specifically, in this embodiment of the present invention, twoidentifiers, that is, a first identifier and a second identifier, may bepreconfigured for the initial P-CSCF, where the first identifierincludes an IP address of the initial P-CSCF, and the second identifierincludes an IP address of a P-CSCF except the initial P-CSCF. The firstidentifier is an IP address advertised by the initial P-CSCF, and thesecond identifier is an IP address of another P-CSCF (which iscorresponding to the available P-CSCF in S102), except the initialP-CSCF, in the P-CSCF pool. When it is detected in S102 that the initialP-CSCF is faulty, the notification message may be directly sent to theavailable P-CSCF according to the configured second identifier.

The configuring two identifiers for the initial P-CSCF may bespecifically configuring, on a DNS (domain name system) server, thefirst identifier and the second identifier according to a host name ofthe initial P-CSCF.

S102 may specifically include: acquiring the first identifier and thesecond identifier that are configured for the initial P-CSCF, which maybe specifically querying on the DNS server by using the host name of theinitial P-CSCF, to acquire the first identifier and the secondidentifier; if it is detected, according to the acquired firstidentifier, that the initial P-CSCF corresponding to the firstidentifier is faulty, using a P-CSCF corresponding to the secondidentifier as the available P-CSCF, for example, if a heartbeat messageis sent by using the first identifier and no response message isnormally received, it may be determined that the initial P-CSCFcorresponding to the first identifier is faulty; and sending thenotification message to the available P-CSCF according to the secondidentifier. That is, the notification message is sent according to theconfigured second identifier. It should be noted that the notificationmessage further carries the user name of the user terminal, so that theavailable P-CSCF initiates, according to the user name, a procedure oftriggering the user terminal to re-register with the P-CSCF.

S103. Optionally, when a registration complete message sent by theP-CSCF with which the user terminal re-registers is received, deliverthe called request to the re-registered P-CSCF to bear a called serviceof the user terminal, where the available P-CSCF triggers, by using apolicy and charging rules function PCRF (policy and charging rulesfunction) entity, the user terminal to re-register with the P-CSCF.

The available P-CSCF may learn, according to the redundancy identifierin the notification message, that the current P-CSCF with which the userterminal registers is faulty, and initiate the procedure of triggeringthe user terminal to re-register with the P-CSCF. Specifically, theavailable P-CSCF may instruct, by using the policy and charging rulesfunction (PCRF) entity that manages the user terminal and by using apath of a gateway connected to the user terminal, the user terminal tore-register with a new P-CSCF, so that the S-CSCF delivers the calledrequest to the new P-CSCF, and the new P-CSCF bears the called serviceof the user terminal. The available P-CSCF may alternatively determine,when receiving the called request of the user terminal and whendetermining that the available P-CSCF does not store the registrationdata of the called user, that the current P-CSCF with which the userterminal registers is faulty, and need to initiate the procedure oftriggering the user terminal to re-register with the P-CSCF.

Further, the delivering the called request to the re-registered P-CSCFto bear a called service of the user terminal includes: sending thecalled request to the re-registered P-CSCF, so that the re-registeredP-CSCF sends the called request to the user terminal to perform thecalled service. That is, the S-CSCF sends the called request to there-registered P-CSCF, and then the re-registered P-CSCF sends the calledrequest to the user terminal to complete the called service.

In this embodiment of the present invention, after a called request isreceived, if it is detected that a P-CSCF with which a user terminalcorresponding to the called request currently registers is faulty, acorresponding message that carries a redundancy identifier is generatedto finally trigger the terminal to re-register with a P-CSCF, and acalled service of the user terminal is borne in the re-registeredP-CSCF, which avoids problems in the prior art that a dual-host fault iscaused because heartbeat detection needs to be performed between aprimary network element and a secondary network element and processingis complex because a same IP needs to be presented to the outside. Inaddition, fault recovery can be quickly completed in an existing networkarchitecture.

Referring to FIG. 2A, FIG. 2A is a schematic flowchart of Embodiment 2of a method for recovering a called service of a terminal according tothe present invention. The method in this embodiment of the presentinvention may be implemented in a P-CSCF, and the P-CSCF triggers,according to a notification message sent by a front-end S-CSCF, a userterminal to re-register with a P-CSCF. Specifically, in this embodimentof the present invention, the method includes the following steps:

S201: Receive a notification message that is sent by a serving-callsession control function S-CSCF entity and carries a user name, wherethe user name includes an identifier of a user terminal corresponding toa called request received by the S-CSCF, that is, an identifier of auser terminal of a called party, and may be specifically an IP address,a user service permission, other user configuration information, and thelike of the user terminal used as the called party.

S202: Generate, if it is found, by means of parsing, that thenotification message further includes a redundancy identifier, areselection request that carries a P-CSCF re-select flag and the username.

The notification message that carries the redundancy identifier isgenerated when a P-CSCF with which the user terminal corresponding tothe called request received by the S-CSCF registers is faulty, and theredundancy identifier is used to instruct to trigger the user terminalto re-register with a P-CSCF. That is, when the P-CSCF with which theuser terminal used as the called party registers is faulty, are-registration procedure is triggered.

For a process in which the S-CSCF generates the notification messagethat includes the redundancy identifier, refer to descriptions inEmbodiment 1 of the foregoing method. In this embodiment of the presentinvention, a P-CSCF in a P-CSCF pool performs related steps, and theP-CSCF is corresponding to the available P-CSCF in Embodiment 1.

However, if the notification message received in S201 includes noredundancy identifier, a called service of a corresponding user terminalmay be borne according to the user name in the notification message.

S203: Send the reselection request to a policy and charging rulesfunction PCRF entity that manages the user terminal indicated by theuser name, so that the PCRF instructs, according to the P-CSCF re-selectflag, the user terminal indicated by the user name to reselect a P-CSCFto bear a called service of the user terminal.

The reselection request that is generated in S202 and carries the P-CSCFre-select flag and the user name may be specifically an STR(session-termination-request), where the STR carries a defined P-CSCFre-select flag, and the user name is used to instruct the PCRF todetermine a user terminal that needs to perform reselection andregistration. The STR is sent to the PCRF in S203.

Specifically, when the reselection request is sent in S203, theavailable P-CSCF may not know the PCRF to which the user terminalcorresponding to the user name belongs. In this case, S203 specificallyincludes: sending the reselection request to a Diameter routing agentDRA (Diameter routing agent), so that the DRA sends, according to theuser name in the reselection request, the reselection request to thePCRF that manages the user terminal indicated by the user name. That is,the available P-CSCF may first send the STR to the DRA, and then, theDRA determines, according to the user name in the STR, the PCRF of theuser terminal corresponding to the user name.

Further, before S202 is performed, the method may further include:

determining whether the user terminal indicated by the user nameregisters with a local end; and

if the user terminal does not register with the local end, performingS202. However, if the user terminal has registered with the local end, aregistration complete message may be directly sent to the S-CSCF, andthe user name of the user terminal and a host name of the local end areregistered in the S-CSCF, so that the S-CSCF sends the called request ofthe user terminal to the local end, and the local end bears the calledservice of the user terminal used as the called party.

That is, only when the user terminal does not register with theavailable P-CSCF, whether to initiate a recovery procedure isdetermined, so that the user terminal re-registers with a P-CSCF.

The available P-CSCF may instruct, by using the PCRF that manages theuser terminal and by using a notification path of a gateway connected tothe user terminal, the user terminal to re-register with a new P-CSCF,so that the S-CSCF delivers the called request of the user terminal tothe new P-CSCF, and the new P-CSCF bears the called service of the userterminal. After the user terminal is instructed to re-register with thenew P-CSCF, the user terminal may select the available P-CSCF.Therefore, this embodiment of the present invention may further includethe following S204.

S204: When a registration request of the user terminal is received, senda registration complete message to an S-CSCF to which the user terminalbelongs, to complete registration of the user terminal.

The user terminal may complete registration with the current P-CSCF byusing an existing registration procedure. After determining that theuser terminal successfully registers with the P-CSCF, the P-CSCF sendsthe registration complete message to a front-end S-CSCF, so as toinstruct the front-end S-CSCF to deliver the received called request tothe current P-CSCF to bear the called service of the user terminal.

In this embodiment of the present invention, when a P-CSCF with which auser terminal currently registers is faulty, the terminal is finallytriggered, according to a message that carries a redundancy identifier,to re-register with a P-CSCF, and a called service of the user terminalis borne in the re-registered P-CSCF, which avoids problems in the priorart that a dual-host fault is caused because heartbeat detection needsto be performed between a primary network element and a secondarynetwork element and processing is complex because a same IP needs to bepresented to the outside. In addition, fault recovery can be quicklycompleted in an existing network architecture.

This embodiment of the present invention further provides another methodfor recovering a called service of a terminal, as shown in FIG. 2B. Themethod shown in FIG. 2B may be implemented in a P-CSCF, andspecifically, the method includes the following steps:

S201′: Receive a called request of a user terminal.

In Step 201′, a called request of the user terminal that is sent by anS-CSCF or an IBCF may be received.

S202′: Determine that no registration data of a called user is stored.

It should be noted that, in step S202′, a P-CSCF determines whether theP-CSCF stores the registration data of the called user, and performsstep S203′ when determining that the P-CSCF does not store theregistration data of the called user.

S203′: Send, to a PCRF that manages the user terminal, a request fortriggering the user terminal to re-initiate IMS registration.

It should be noted that the request for triggering the user terminal tore-initiate the IMS registration may be a request that carries are-registration identifier, where the re-registration identifier is usedto trigger the user terminal to re-initiate the IMS registration. As anexample instead of a limitation, the request that carries there-registration identifier may be an STR or an AAR (authorization andauthentication request).

Referring to FIG. 3, FIG. 3 is a schematic flowchart of Embodiment 3 ofa method for recovering a called service of a terminal according to thepresent invention. The method in this embodiment of the presentinvention may be applied to a policy and charging rules function (PCRF)entity that manages a user terminal. When receiving a reselectionrequest, such as an STR that carries a P-CSCF re-select flag, that issent by a P-CSCF, the PCRF performs steps of the method in thisembodiment of the present invention. Specifically, the method includesthe following steps:

S301: Generate a registration triggering request when a reselectionrequest that is sent by a P-CSCF and carries a P-CSCF re-select flag anda user name is received, where the user name includes an identifier of auser terminal corresponding to a called request received by an S-CSCF,that is, an identifier of a user terminal of a called party, and may bespecifically an IP address, a user service permission, other userconfiguration information, and the like of the user terminal used as thecalled party.

S302: Send the generated registration triggering request to a gatewayconnected to the user terminal indicated by the user name, so that thegateway triggers the user terminal indicated by the user name tore-register with a P-CSCF to bear a called service of the user terminal.

The reselection request is generated by the P-CSCF according to anotification message that is sent by the S-CSCF and carries the username and a redundancy identifier, where the redundancy identifier isused to instruct to trigger the user terminal indicated by the user nameto re-register with the P-CSCF. The reselection request may be an STR orthe like, and for a specific process of generating the reselectionrequest, refer to descriptions in Embodiment 2.

After receiving the reselection request such as the STR that carries theP-CSCF re-select flag, the PCRF needs to perform a procedure ofrecovering the called service of the user terminal corresponding to theuser name, that is, generating the registration triggering request andsending the registration triggering request to the gateway of the userterminal corresponding to the user name. The gateway may be a P-GW(packet data network gateway) or an S-GW (serving gateway). The gatewaydirectly triggers the user terminal to reselect a new P-CSCF.

Specifically, S301 may specifically include:

when the reselection request that is sent by the P-CSCF and carries theP-CSCF re-select flag and the user name is received, generating aregistration triggering request that carries a session release message,where the session release message is used to instruct the gatewayconnected to the user terminal indicated by the user name to request amobility management entity (MME) to delete a user bearer of a userterminal.

The registration triggering request may be an RAR (re-authenticationrequest) that carries a Session-Release-Cause AVP (attribute-valuepair), that is, an attribute field of Session-Release-Cause and a fieldvalue are carried in the RAR to instruct the gateway to request todelete all bearers of the user terminal. The gateway directly requeststo release an IMS (IP multimedia subsystem) PDN (packet data network) ofthe user terminal corresponding to the user name, that is, delete acommunications network that bears IMS signaling of the user terminal.

The user terminal loses a connection after the MME deletes the IMS PDN.The user terminal detects an access failure, and automatically performsa new registration procedure to complete registration with the P-CSCFand the like, to implement network accessing. The user terminal selectsan available third P-CSCF3 and initiates SIP (Session InitiationProtocol) initial registration with the third P-CSCF. After receiving aregistration request of the user terminal, the third P-CSCF sends amessage to an S-CSCF to which the user terminal belongs, to complete theregistration request. The third P-CSCF may determine, by using anI-CSCF, the S-CSCF to which the user terminal belongs, and then send aregistration complete message to the found S-CSCF to which the userterminal belongs, to complete the registration request. Then, the S-CSCFdelivers the called request of the user terminal to the third P-CSCF tobear the called service.

Alternatively, S301 includes:

when the reselection request that is sent by the P-CSCF and carries theP-CSCF re-select flag and the user name is received, generating aregistration triggering request that carries update P-CSCF addressinformation, where the update P-CSCF address information is used toinstruct the gateway connected to the user terminal indicated by theuser name to generate a list of available P-CSCF addresses and send thelist of the available P-CSCF addresses to the user terminal indicated bythe user name.

The registration triggering request is an RAR that carries an updateP-CSCF address request. After receiving the RAR, the gateway sends anupdate PDP (Packet Data Protocol) context message (Update PDP Context)to the user terminal, so that the user terminal completesre-registration. After receiving the Update PDP Context, the userterminal updates a local P-CSCF list according to the list of theavailable P-CSCF addresses in the Update PDP Context, checks whether aninitial P-CSCF with which a local end registers is in the list, and ifthe initial P-CSCF with which the local end registers is not in thelist, the user terminal initiates a procedure of re-registering with aP-CSCF, which may be specifically selecting an available third P-CSCF3from a new P-CSCF list (list) delivered by the gateway and registeringwith the third P-CSCF3 to bear the called service of the user terminal.The third P-CSCF may determine, by using an I-CSCF, an S-CSCF to whichthe user terminal belongs, and then send a registration complete messageto the found S-CSCF to which the user terminal belongs, to complete theregistration request. Then, the S-CSCF delivers the called request ofthe user terminal to the third P-CSCF to bear the called service.

In this embodiment of the present invention, when a P-CSCF with which auser terminal currently registers is faulty, the terminal is finallytriggered, according to a message that carries a redundancy identifier,to re-register with a P-CSCF, and a called service of the user terminalis borne in the re-registered P-CSCF, which avoids problems in the priorart that a dual-host fault is caused because heartbeat detection needsto be performed between a primary network element and a secondarynetwork element and processing is complex because a same IP needs to bepresented to the outside. In addition, fault recovery can be quicklycompleted in an existing network architecture.

Referring to FIG. 4, FIG. 4 is a schematic flowchart of Embodiment 4 ofa method for recovering a called service of a terminal according to thepresent invention. The method in this embodiment of the presentinvention may be applied to, for example, a P-GW or an S-GW. Whenreceiving a registration triggering request, such as an RAR, that issent by a PCRF, the P-GW or the S-GW performs steps of the method inthis embodiment of the present invention. Specifically, the methodincludes the following steps:

S401: Receive a registration triggering request that is sent by a policyand charging rules function PCRF entity and carries a user name, wherethe user name includes an identifier of a user terminal corresponding toa called request received by an S-CSCF, that is, an identifier of a userterminal used as a called party, and may be specifically an IP address,a user service permission, other user configuration information, and thelike of the user terminal used as the called party.

S402: Trigger the user terminal indicated by the user name tore-register with a P-CSCF to bear a called service of the user terminal.

The registration triggering request is generated when the PCRF receivesa reselection request that is sent by a P-CSCF and carries a P-CSCFre-select flag and the user name, and the reselection request isgenerated by the P-CSCF according to a notification message that is sentby the S-CSCF and carries the user name and a redundancy identifier,where the redundancy identifier is used to instruct to trigger the userterminal indicated by the user name to re-register with the P-CSCF.

For processes of generating the reselection request and the registrationtriggering request, refer to descriptions in Embodiment 2 and Embodiment3 accordingly.

Specifically, S402 may specifically include:

when the registration triggering request carries a session releasemessage, sending, to an MME, a release request that carries the username, so that the MME deletes a user bearer of the user terminalindicated by the user name; or

when the registration triggering request carries update P-CSCF addressinformation, acquiring a list of available P-CSCF addresses and sendingthe list of the available P-CSCF addresses to the user terminalindicated by the user name, so that the user terminal selects a P-CSCFfrom the list of the available P-CSCF addresses and registers with theselected P-CSCF.

After receiving an RAR that is sent by the PCRF and carries aSession-Release-Cause AVP, the gateway instructs the MME to delete anIMS PDN of a user, and triggers the user terminal to re-register with aP-CSCF. When receiving an RAR that is sent by the PCRF and carries anupdate P-CSCF address request, the gateway acquires an Update PDPContext message and sends the Update PDP Context message to the userterminal to trigger the user terminal to update a local P-CSCF listaccording to the list of the available P-CSCF addresses in the UpdatePDP Context message, and after determining that an updated local P-CSCFlist does not include an initial P-CSCF with which a local end hasregistered, selects a new P-CSCF and registers with the selected P-CSCFto complete re-registration.

In this embodiment of the present invention, when a P-CSCF with which auser terminal currently registers is faulty, the terminal is finallytriggered, according to a message that carries a redundancy identifier,to re-register with a P-CSCF, and a called service of the user terminalis borne in the re-registered P-CSCF, which avoids problems in the priorart that a dual-host fault is caused because heartbeat detection needsto be performed between a primary network element and a secondarynetwork element and processing is complex because a same IP needs to bepresented to the outside. In addition, fault recovery can be quicklycompleted in an existing network architecture.

Referring to FIG. 5, FIG. 5 is a schematic flowchart of Embodiment 5 ofa method for recovering a called service of a terminal according to thepresent invention. The method in this embodiment of the presentinvention may be applied to a user terminal. When determining that anIMS PDN in an MME is deleted or a list of available P-CSCF addressesthat is sent by a P-GW or an S-GW is received, the user terminalperforms related steps of the method in this embodiment of the presentinvention. Specifically, the method includes the following steps:

S501: When an access failure is detected, initiate a registrationrequest for registering with a P-CSCF, so that a re-registered P-CSCFbears a called service when an initial P-CSCF is faulty.

A user terminal loses a connection after an MME deletes an IMS PDN. Theuser terminal detects the access failure, and automatically performs anew registration procedure to complete registration with the P-CSCF andthe like, to implement network accessing. The user terminal selects anavailable third P-CSCF3 and initiates SIP initial registration with thethird P-CSCF. After receiving the registration request of a userterminal, the third P-CSCF sends a message to an S-CSCF to which theuser terminal belongs, to complete the registration request. The thirdP-CSCF may determine, by using an I-CSCF, the S-CSCF to which the userterminal belongs, and then send a registration complete message to thefound S-CSCF to which the user terminal belongs, to complete theregistration request. Then, the S-CSCF delivers a called request of theuser to the third P-CSCF to bear the called service.

S502: When a list of available P-CSCF addresses that is sent by agateway is received, select a P-CSCF from the list of the availableP-CSCF addresses and register with the selected P-CSCF, so that there-registered P-CSCF bears the called service when the initial P-CSCF isfaulty.

Specifically, S502 may include: when the list of the available P-CSCFaddresses that is sent by the gateway is received, determining whetherthe list of the available P-CSCF addresses includes a host name of theinitial P-CSCF with which the user terminal currently registers; and ifthe list of the available P-CSCF addresses does not include the hostname of the initial P-CSCF, selecting the P-CSCF from the list of theavailable P-CSCF addresses and registering with the selected P-CSCF.

The registration triggering request is an RAR that carries an updateP-CSCF address request. After receiving the RAR, the gateway sends anUpdate PDP Context message to the user terminal, so that the userterminal completes re-registration. After receiving the Update PDPContext, the user terminal updates a local P-CSCF list according to thelist of the available P-CSCF addresses in the Update PDP Context, checkswhether an initial P-CSCF with which a local end registers is in thelist, and if not, the user terminal initiates a procedure ofre-registering with a P-CSCF, which may be specifically selecting theavailable third P-CSCF3 from a new P-CSCF list delivered by the gatewayand registering with the third P-CSCF3 to bear the called service of theuser terminal. The third P-CSCF may determine, by using an I-CSCF, theS-CSCF to which the user terminal belongs, and then send a registrationcomplete message to the found S-CSCF to which the user terminal belongs,to complete the registration request. Then, the S-CSCF delivers thecalled request of the user terminal to the third P-CSCF to bear thecalled service.

It should be noted that S501 and S502 are not performed in sequence. Ifaccess fails are first detected, then S502 is performed; or if the listof the available P-CSCF addresses sent by the gateway is first detectedafter being received, then S501 is performed.

In this embodiment of the present invention, when a P-CSCF with which auser terminal currently registers is faulty, the terminal canre-register with a new P-CSCF according to a structure, on a networkside, for recovery processing based on a message that carries aredundancy identifier, and carry a called service of the user terminalin the new P-CSCF, which avoids problems in the prior art that adual-host fault is caused because heartbeat detection needs to beperformed between a primary network element and a secondary networkelement and processing is complex because a same IP needs to bepresented to the outside. In addition, fault recovery can be quicklycompleted in an existing network architecture.

Referring to FIG. 6, FIG. 6 is a schematic flowchart of Embodiment 6 ofa method for recovering a called service of a terminal according to thepresent invention. In the method in this embodiment of the presentinvention, by using a user terminal UE, an S-CSCF, a P-CSCF, a PCRF, anda gateway, quick recovery of a called service of the user terminal isimplemented when a P-CSCF with which the user terminal currentlyregisters is faulty. Specifically, as shown in FIG. 6, the methodincludes the following steps:

S11: After receiving a called request of a user terminal, an S-CSCFqueries an initial P-CSCF with which the user terminal currentlyregisters; the S-CSCF finds, by means of querying, an IP address of theP-CSCF according to a host name of the P-CSCF, and configures, on a DNS,two IPs, namely, an IP1 and an IP2 that are respectively correspondingto a P-CSCF1 and a P-CSCF2, for a host name of the P-CSCF1, that is, theinitial P-CSCF.

S12: The S-CSCF detects that the initial P-CSCF is faulty, selects anavailable P-CSCF, and sends, to the available P-CSCF, a notificationmessage that carries a redundancy identifier, where the redundancyidentifier is used to instruct the available P-CSCF to trigger the userterminal to re-register with the P-CSCF.

After sensing that the P-CSCF (P-CSCF1) corresponding to the IP1 isfaulty, the S-CSCF sends, to the available P-CSCF (P-CSCF2)corresponding to the IP2, a NOTIFY that carries the redundancyidentifier to instruct the user terminal to re-register with the P-CSCF.

S13: After receiving the notification message that carries theredundancy identifier and a user name, the P-CSCF2 generates areselection request that carries a P-CSCF re-select flag and the username, and sends the reselection request to a PCRF, where the PCRF isconfigured to manage a user terminal indicated by the user name.

When detecting that the message carries the redundancy identifier, orthe message carries the redundancy identifier and does not register witha local end, the P-CSCF2 initiates a redundancy procedure. The P-CSCF2sends an STR (that is, the reselection request) to the PCRF, where theSTR carries a self-defined P-CSCF re-select flag. If the P-CSCF2 doesnot know the PCRF of a user terminal, the STR is first sent to a DRA,and the DRA routes the STR to the PCRF on which the user terminal islocated.

S14: After receiving the reselection request that is sent by the P-CSCFand carries the P-CSCF re-select flag and the user name, the PCRFgenerates a registration triggering request and sends the registrationtriggering request to a gateway, where the gateway is an S-GW or a P-GWand is connected to the user terminal.

After receiving the STR that carries the P-CSCF re-select flag, the PCRFneeds to perform a redundancy procedure. The PCRF sends an RAR to theP/S-GW to request to delete all bearers of the user terminal.

S15: After receiving the registration triggering request that is sent bythe PCRF entity and carries the user name, the P/S-GW triggers the userterminal indicated by the user name to re-register with the P-CSCF.

After receiving the RAR sent by the PCRF, the P/S-GW instructs the MMEto delete an IMS PDN of the user, and triggers the user to performre-registration.

S16: The user terminal selects an available P-CSCF3, and initiates SIPinitial registration with the P-CSCF3.

S17: After receiving a registration request of the user terminal, theP-CSCF3 initiates SIP registration with an S-CSCF to which a userterminal belongs, to complete the registration request, and the P-CSCF3may determine, in a manner of querying an I-CSCF, the S-CSCF to whichthe user terminal belongs.

S18: The S-CSCF delivers the called request to the P-CSCF3.

S19: The P-CSCF3 sends the called request to a UE to bear a calledservice of the user terminal according to the called request, so as tocomplete the called service of the user terminal.

In this embodiment of the present invention, when a P-CSCF with which auser terminal currently registers is faulty, the terminal is finallytriggered, according to a message that carries a redundancy identifier,to re-register with a P-CSCF, and a called service of the user terminalis borne in the re-registered P-CSCF, which avoids problems in the priorart that a dual-host fault is caused because heartbeat detection needsto be performed between a primary network element and a secondarynetwork element and processing is complex because a same IP needs to bepresented to the outside. In addition, fault recovery can be quicklycompleted in an existing network architecture.

Referring to FIG. 7, FIG. 7 is a schematic flowchart of Embodiment 7 ofa method for recovering a called service of a terminal according to thepresent invention. In the method in this embodiment of the presentinvention, by using a user terminal, an S-CSCF, a P-CSCF, a PCRF, and agateway, quick recovery of a called service of the user terminal isimplemented when a P-CSCF with which the user terminal currentlyregisters is faulty. Specifically, as shown in FIG. 7, the methodincludes the following steps:

S21: After receiving a called request, an S-CSCF queries an initialP-CSCF with which a user terminal corresponding to the called requestcurrently registers, where the initial P-CSCF is an initial P-CSCF of auser terminal used as a called party; the S-CSCF finds, by means ofquerying, an IP address of the P-CSCF according to a host name of theP-CSCF, and configures, on a DNS, two IPs, namely, an IP1 and an IP2that are respectively corresponding to a P-CSCF1 and a P-CSCF2, for ahost name of the P-CSCF1, that is, the initial P-CSCF.

S22: The S-CSCF detects that the initial P-CSCF is faulty, selects anavailable P-CSCF, and sends, to the available P-CSCF, a notificationmessage that carries a redundancy identifier, where the redundancyidentifier is used to instruct the available P-CSCF to trigger the userterminal to re-register with the P-CSCF.

After sensing that the P-CSCF (P-CSCF1) corresponding to the IP1 isfaulty, the S-CSCF sends, to the available P-CSCF (P-CSCF2)corresponding to the IP2, a NOTIFY that carries the redundancyidentifier to instruct the user terminal to re-register with the P-CSCF.

S23: After receiving the notification message that carries theredundancy identifier and a user name, the P-CSCF2 generates areselection request that carries a P-CSCF re-select flag and the username, and sends the reselection request to a PCRF, where the PCRF isconfigured to manage a user terminal indicated by the user name.

When detecting that the message carries the redundancy identifier, orthe message carries the redundancy identifier and does not register witha local end, the P-CSCF2 initiates a redundancy procedure. The P-CSCF2sends an STR (that is, the reselection request) to the PCRF, where theSTR carries a self-defined P-CSCF re-select flag. If the P-CSCF2 doesnot know the PCRF of a user terminal, the STR is first sent to a DRA,and the DRA routes the STR to the PCRF on which the user terminal islocated.

S24: After receiving the reselection request that is sent by the P-CSCFand carries the P-CSCF re-select flag and the user name, the PCRFgenerates a registration triggering request and sends the registrationtriggering request to a gateway, where the gateway is an S-GW or a P-GWand is connected to the user terminal.

After receiving the STR that carries the P-CSCF re-select flag, the PCRFneeds to perform a redundancy procedure. A method for redundancy by thePCRF is sending an RAR to the P-GW, where the RAR carries an updateP-CSCF address request, and the request may be proprietary.

S25: When the registration triggering request carries update P-CSCFaddress information, the P/S-GW acquires a list of available P-CSCFaddresses, and sends the list of the available P-CSCF addresses to theuser terminal indicated by the user name.

After receiving the RAR, the P/S-GW sends an Update PDP Context messageto the user terminal, where the Update PDP Context message includes thelist of the available P-CSCF addresses.

S26: When receiving the list of the available P-CSCF addresses that issent by the gateway, the user terminal selects a P-CSCF from the list ofthe available P-CSCF addresses, so as to bear, by using there-registered P-CSCF, a called service when the initial P-CSCF isfaulty.

After receiving the Update PDP Context, the user terminal updates aP-CSCF list, and checks whether the P-CSCF1 with which the user terminalregisters is in the list; and if not, a UE initiates a re-registrationprocedure, and selects an available P-CSCF3 from a new P-CSCF Listdelivered by the P-GW, to perform registration.

S27: Send a registration request and register with a selected P-CSCF3.

S28: After receiving a registration request of the user terminal, theP-CSCF3 sends a message to an S-CSCF to which a user terminal belongs,to complete the registration request, where the P-CSCF3 may determine,in a manner of querying an I-CSCF, the S-CSCF to which the user terminalbelongs.

S29: The S-CSCF delivers the called request to the P-CSCF3.

S210: The P-CSCF3 sends the called request to a UE to bear a calledservice of the user terminal according to the called request, so as tocomplete the called service of the user terminal.

In this embodiment of the present invention, when a P-CSCF with which auser terminal currently registers is faulty, the terminal is finallytriggered, according to a message that carries a redundancy identifier,to re-register with a P-CSCF, and a called service of the user terminalis borne in the re-registered P-CSCF, which avoids problems in the priorart that a dual-host fault is caused because heartbeat detection needsto be performed between a primary network element and a secondarynetwork element and processing is complex because a same IP needs to bepresented to the outside. In addition, fault recovery can be quicklycompleted in an existing network architecture.

FIG. 8 is a schematic flowchart of a method for recovering a calledservice of a terminal according to an embodiment of the presentinvention. In the method in this embodiment of the present invention, byusing a user terminal UE, an S-CSCF, a P-CSCF, a PCRF, and a gateway,the user terminal is triggered to perform re-registration when a P-CSCFwith which the user terminal currently registers is faulty.Specifically, as shown in FIG. 8, the method includes the followingsteps:

S801: After receiving a called request of a user terminal, an S-CSCFacquires an address of a P-CSCF1 that is stored when a called usersuccessfully registers with the P-CSCF1.

For the address of the P-CSCF, an address or addresses of one or moresecondary devices, for example, an address of a P-CSCF2, may bepreconfigured on the S-CSCF. Another manner of acquiring an address of asecondary P-CSCF is: when a stored P-CSCF address is a domain name, anaddress of a secondary P-CSCF2 is acquired by querying on a DNS.

If the S-CSCF detects (for example, by means of options heartbeatdetection) that the P-CSCF is faulty, the S-CSCF selects the secondaryP-CSCF2 during routing.

S802: The S-CSCF sends the called request to an available P-CSCF2.

S803: After receiving the called request, the P-CSCF2 finds that noregistration data of the called user is stored, and returns an errorresponse to the S-CSCF to refuse a current call.

Specifically, when finding that the P-CSCF2 does not store theregistration data of the called user, the P-SCCF2 returns the errorresponse to the S-CSCF.

S804: The P-CSCF2 sends, to a PCRF, a request for triggering the userterminal to re-initiate IMS registration.

Optionally, the request may carry a re-registration identifier, wherethe re-registration identifier is used to trigger the user terminal tore-initiate the IMS registration.

The request sent by the P-CSCF2 to the PCRF may be an STR or an AAR. Itshould be noted that the P-CSCF2 may also send, to a DRA, the requestfor triggering the user terminal to re-initiate the IMS registration,and the DRA routes, to the PCRF to which the user terminal belongs, therequest for triggering the user terminal to re-initiate the IMSregistration.

S805: After receiving the request for triggering the user terminal tore-initiate the IMS registration, the PCRF generates a registrationtriggering request and sends the registration triggering request to agateway, where the gateway may be an S-GW or a P-GW.

S806: When receiving the registration triggering request sent by thePCRF, the P-GW or the S-GW triggers the user terminal to performre-registration.

Specifically, the P-GW or the S-GW instructs an MME to delete an IMS PDNof the user, and triggers the user to perform re-registration.

S807: The user terminal selects an available P-CSCF, for example, theuser terminal selects a P-CSCF3, and sends a SIP initial registrationrequest to the P-CSCF3.

S808: After the P-CSCF3 receives the registration request of the userterminal, a subsequent procedure is the same as a normal registrationprocedure, and after registration is completed, the user may normallyprocess a service.

In this embodiment of the present invention, when a P-CSCF with which auser terminal currently registers is faulty, an S-CSCF finally triggers,by using a secondary P-CSCF, the terminal to perform re-registration, sothat a service is recovered after a user of the terminal who needs touse the service completes registration.

FIG. 9 is a schematic flowchart of a method for recovering a calledservice of a terminal according to an embodiment of the presentinvention. In the method in this embodiment of the present invention, byusing a user terminal UE, an IBCF, a P-CSCF, a PCRF, and a gateway, theuser terminal is triggered to perform re-registration when a P-CSCF withwhich the user terminal currently registers is faulty. Specifically, asshown in FIG. 9, the method includes the following steps:

S901: After receiving a called request of a user terminal, an IBCFacquires an address of a next-hop P-CSCF1 from a requested route headerfield.

For the address of the P-CSCF, an address or addresses of one or moresecondary devices, for example, an address of a P-CSCF2, may bepreconfigured on the IBCF. Another manner of acquiring an address of asecondary P-CSCF is: when a stored P-CSCF address is a domain name, anaddress of a secondary P-CSCF2 is acquired by querying on a DNS.

When detecting (for example, by means of options heartbeat detection)that the P-CSCF1 is faulty, the IBCF selects the secondary P-CSCF2.

S902: The IBCF sends the called request to the available P-CSCF2.

S903: After receiving the called request, the P-CSCF2 finds that noregistration data of a called user is stored, and returns an errorresponse to the IBCF to refuse a current call.

Specifically, when finding that the P-CSCF2 does not store theregistration data of the called user, the P-SCCF2 returns the errorresponse to the S-CSCF.

S904: The P-CSCF2 sends, to a PCRF, a request for triggering the userterminal to re-initiate IMS registration.

Optionally, the request may carry a re-registration identifier, wherethe re-registration identifier is used to trigger the user terminal tore-initiate the IMS registration.

The request sent by the P-CSCF2 to the PCRF may be an STR or an AAR. Itshould be noted that the P-CSCF2 may also send, to a DRA, the requestfor triggering the user terminal to re-initiate the IMS registration,and the DRA routes, to the PCRF to which the user terminal belongs, therequest for triggering the user terminal to re-initiate the IMSregistration.

S905: After receiving the request for triggering the user terminal tore-initiate the IMS registration, the PCRF generates a registrationtriggering request and sends the registration triggering request to agateway, where the gateway may be an S-GW or a P-GW.

S906: When receiving the registration triggering request sent by thePCRF, the P-GW or the S-GW triggers the user terminal to performre-registration.

Specifically, the P-GW or the S-GW instructs an MME to delete an IMS PDNof the user, and triggers the user to perform re-registration.

S907: The user terminal selects an available P-CSCF, for example, theterminal selects a P-CSCF3, and initiates a SIP initial registrationrequest to the P-CSCF3.

S908: After the P-CSCF3 receives the registration request of the userterminal, a subsequent procedure is the same as a normal registrationprocedure, and after registration is completed, the user may normallyprocess a service.

In this embodiment of the present invention, when a P-CSCF with which auser terminal currently registers is faulty, an S-CSCF finally triggers,by using a secondary P-CSCF, the terminal to perform re-registration, sothat a service is recovered after a user of the terminal who needs touse the service completes registration.

The following describes in detail apparatuses for recovering a calledservice of a terminal and a system thereof according to embodiments ofthe present invention.

Referring to FIG. 10, FIG. 10 is a schematic structural diagram ofEmbodiment 1 of an apparatus for recovering a called service of aterminal according to the present invention. The apparatus in thisembodiment of the present invention may be an S-CSCF or an IBCF.Specifically, the apparatus includes:

a querying module 11, configured to: when a called request of a userterminal is received, query an initial proxy-call session controlfunction P-CSCF entity with which the user terminal currently registers;and

a processing module 12, configured to: if it is detected that theinitial P-CSCF is faulty, select an available P-CSCF and send anotification message to the available P-CSCF to trigger the userterminal to re-register with the P-CSCF.

In a possible implementation manner, the processing module 12 may bespecifically configured to: after selecting the available P-CSCF, send,to the available P-CSCF, a notification message that carries aredundancy identifier, where the redundancy identifier is used toinstruct the available P-SCCF to trigger the user terminal tore-register with the P-CSCF. In another possible implementation manner,the processing module 12 may be specifically configured to: afterselecting the available P-CSCF, send the called request of the userterminal to the available P-CSCF, so as to trigger, when the availableP-CSCF determines that no registration data of a called user is stored,the user terminal to re-initiate IMS registration.

Optionally, the apparatus may further include an allocation module 13.The allocation module 13 is configured to: when a registration completemessage sent by the P-CSCF with which the user terminal re-registers isreceived, deliver the called request to the re-registered P-CSCF to beara called service of the user terminal.

The available P-CSCF triggers, by using a PCRF, the user terminal tore-register with the P-CSCF.

After the user terminal registers with the P-CSCF, the P-CSCF sendscorresponding registration complete information to an S-CSCF, and theS-CSCF performs authentication, and performs processing such asregistering a user name of the user terminal and a host name of theP-CSCF with which the user terminal registers; therefore, according to auser name (a user name of a user terminal used as a called party) of theuser terminal corresponding to the called request, the querying module11 may query and determine the initial P-CSCF with which the userterminal currently registers. The user name of the user terminal is usedto identify the user terminal, and may be specifically an IP address, auser service permission, other user configuration information, and thelike of the user terminal.

The processing module 12 may specifically perform heartbeat detection oneach P-CSCF in a current P-CSCF pool by using a heartbeat mechanism, anddetermine, according to data of the heartbeat detection or according towhether heartbeat data can be normally received, whether the initialP-CSCF with which the user terminal currently registers is faulty, forexample, it may be determined that the initial P-CSCF is faulty when aping command has no response or a detection message fails to be receivedor sent.

When it is detected that the initial P-CSCF is faulty, the processingmodule 12 specifically selects an available P-CSCF from the currentP-CSCF pool. The available P-CSCF may be a P-CSCF that is determined, bymeans of heartbeat detection or other manners, to be not faulty. Theprocessing module 12 may also select a secondary P-CSCF of the initialP-CSCF as the available P-CSCF according to two identifiers configuredfor the initial P-CSCF.

The available P-CSCF may learn, according to the redundancy identifierin the notification message, that the current P-CSCF with which the userterminal registers is faulty, and initiate the procedure of triggeringthe user terminal to re-register with the P-CSCF. Specifically, theavailable P-CSCF may instruct, by using the policy and charging rulesfunction PCRF entity that manages the user terminal and by using a pathof a gateway connected to the user terminal, the user terminal tore-register with a new P-CSCF, so that the allocation module 13 deliversthe called request of the user terminal to the new P-CSCF, and the newP-CSCF bears the called service of the user terminal. The availableP-CSCF may also determine, when receiving the called request of the userterminal and when determining that the available P-CSCF does not storethe registration data of the called user, that the current P-CSCF withwhich the user terminal registers is faulty, and the procedure oftriggering the user terminal to re-register with the P-CSCF needs to beinitiated.

Further, optionally, as shown in FIG. 10, the apparatus may furtherinclude:

a configuration module 14, configured to configure a first identifierand a second identifier for the initial P-CSCF, where the firstidentifier includes an IP address of the initial P-CSCF, and the secondidentifier includes an IP address of a P-CSCF except the initial P-CSCF.

Further, the configuration module 14 is specifically configured toconfigure, on a domain name system DNS server, the first identifier andthe second identifier according to a host name of the initial P-CSCF.

The configuration module 14 may preconfigure two identifiers, that is,the first identifier and the second identifier, for the initial P-CSCF,where the first identifier includes the IP address of the initialP-CSCF, and the second identifier includes the IP address of the P-CSCFexcept the initial P-CSCF. The first identifier is an IP addressadvertised by the initial P-CSCF, and the second identifier is an IPaddress of another P-CSCF, except the initial P-CSCF, in the P-CSCFpool. When the processing module 12 detects that the initial P-CSCF isfaulty, the notification message may be directly sent to the availableP-CSCF according to the second identifier configured by theconfiguration module 14.

Further, optionally, as shown in FIG. 10, the processing module 12 mayspecifically include:

an acquiring unit 121, configured to acquire the first identifier andthe second identifier that are configured for the initial P-CSCF;

a detection unit 122, configured to: if it is detected, according to theacquired first identifier, that the initial P-CSCF corresponding to thefirst identifier is faulty, use a P-CSCF corresponding to the secondidentifier as the available P-CSCF; and

a processing unit 123, configured to send the notification message tothe available P-CSCF according to the second identifier.

That is, the processing module 12 sends the notification messageaccording to the second identifier configured by the configurationmodule 14.

Further, optionally, the allocation module 13 is specifically configuredto send the called request to the re-registered P-CSCF, so that there-registered P-CSCF sends the called request to the user terminal toperform the called service.

In this embodiment of the present invention, after a called request isreceived, if it is detected that a P-CSCF with which a user terminalthat is of a called party and is corresponding to the called requestcurrently registers is faulty, a corresponding message that carries aredundancy identifier is generated to finally trigger the terminal tore-register with a P-CSCF, and a called service of the user terminal isborne in the re-registered P-CSCF, which avoids problems in the priorart that a dual-host fault is caused because heartbeat detection needsto be performed between a primary network element and a secondarynetwork element and processing is complex because a same IP needs to bepresented to the outside. In addition, fault recovery can be quicklycompleted in an existing network architecture.

Referring to FIG. 11A, FIG. 11A is a schematic flowchart of Embodiment 2of an apparatus for recovering a called service of a terminal accordingto the present invention. The apparatus in this embodiment of thepresent invention may be a P-CSCF. Specifically, the apparatus includes:

a receiving module 21, configured to receive a notification message thatis sent by a serving-call session control function S-CSCF entity andcarries a user name, where the user name includes an identifier of auser terminal corresponding to a called request received by the S-CSCF,that is, an identifier of a user terminal of a called party, and may bespecifically an IP address, a user service permission, other userconfiguration information, and the like of the user terminal used as thecalled party;

a processing module 22, configured to generate, if it is found, by meansof parsing, that the notification message further includes a redundancyidentifier, a reselection request that carries a P-CSCF re-select flagand the user name; and

a sending module 23, configured to send the reselection request to aPCRF entity that manages the user terminal indicated by the user name,so that the PCRF instructs, according to the P-CSCF re-select flag, theuser terminal indicated by the user name to reselect a P-CSCF to bear acalled service of the user terminal.

The notification message that carries the redundancy identifier isgenerated by the S-CSCF when a P-CSCF with which the user terminalcorresponding to a received called request registers is faulty, and theredundancy identifier is used to instruct to trigger the user terminalto re-register with a P-CSCF. That is, the notification message isgenerated when the initial P-CSCF of the user terminal of the calledparty is faulty.

For a process in which the S-CSCF generates the notification messagethat includes the redundancy identifier, refer to descriptions inEmbodiment 1 of the foregoing apparatus.

However, if the notification message received by the receiving module 21includes no redundancy identifier, the processing module 22 of theP-CSCF may bear a called service of a corresponding user terminalaccording to the user name in the notification message.

The reselection request that is generated by the processing module 22and carries the P-CSCF re-select flag and the user name may bespecifically an STR, where the STR carries a defined P-CSCF re-selectflag; the sending module 23 sends the STR to the PCRF.

Specifically, when sending the reselection request, the sending module23 may not know the PCRF to which the user terminal corresponding to theuser name belongs. In this case, further, optionally, the sending module23 is specifically configured to send the reselection request to a DRA,so that the DRA sends, according to the user name in the reselectionrequest, the reselection request to the PCRF that manages the userterminal indicated by the user name. That is, the sending module 23 mayfirst send the STR to the DRA, and then, the DRA determines, accordingto the user name in the STR, the PCRF of the user terminal correspondingto the user name.

Further, optionally, as shown in FIG. 11A, the apparatus mayspecifically include:

a determining module 24, configured to: determine whether the userterminal indicated by the user name registers with a local end, and whena result of the determining is that the user terminal does not registerwith the local end, instruct the processing module 22 to perform thegenerating, if it is found, by means of parsing, that the notificationmessage further includes a redundancy identifier, a reselection requestthat carries a P-CSCF re-select flag and the user name.

However, if the determining result of the determining module 24 is thatthe user terminal has registered with the local end, the current P-CSCFmay directly send a registration complete message to the S-CSCF, andregister a user name of the user terminal and a host name of the localend in the S-CSCF, so that the S-CSCF sends the called request receivedto the local end, and the local end bears the called service of the userterminal.

That is, only when the user terminal does not register with theavailable P-CSCF, whether to initiate a recovery procedure isdetermined, so that the user terminal re-registers with a P-CSCF.

The user terminal may be instructed, by using the PCRF that manages theuser terminal and by using a notification path of a gateway connected tothe user terminal, to re-register with a new P-CSCF, so that the S-CSCFdelivers the called request of the user terminal to the new P-CSCF, andthe new P-CSCF bears the called service of the user terminal. After theuser terminal is instructed to re-register with the new P-CSCF, the userterminal may select the available P-CSCF. Therefore, further,optionally, as shown in FIG. 11A, the apparatus may further include:

a registering module 25, configured to: when a registration request ofthe user terminal is received, send a registration complete message toan S-CSCF to which the user terminal belongs, to complete registrationof the user terminal.

The user terminal may complete registration with the current P-CSCF byusing an existing registration procedure. After determining that theuser terminal successfully registers with the P-CSCF, the registeringmodule 25 sends the registration complete message to a front-end S-CSCF,so as to instruct the front-end S-CSCF to deliver the received calledrequest to the current P-CSCF to bear the called service of the userterminal.

Embodiments of the present invention further provide an apparatus forrecovering a called service of a terminal, as shown in FIG. 11B. Theapparatus shown in FIG. 11B may be a P-CSCF, and the apparatus includes:

a receiving module 21′, configured to receive a called request of a userterminal, where

the receiving module 21′ may be specifically configured to receive acalled request of the user terminal that is sent by an S-CSCF or anIBCF;

a processing module 22′, configured to: when the receiving module 21′receives the called request, determine that no registration data of acalled user is stored; and

a sending module 23′, configured to: after the processing module 22′determines that no registration data of the called user is stored, send,to a PCRF that manages the user terminal, a request for triggering theuser terminal to re-initiate IMS registration.

Optionally, the sending module 23′ may be specifically configured tosend, to the PCRF, a request that carries a re-registration identifier,where the re-registration identifier is used to trigger the userterminal to re-initiate the IMS registration. In a possibleimplementation manner, the request that carries the re-registrationidentifier may be an STR or an AAR.

Optionally, the processing module 22′ is specifically configured todetermine that the apparatus shown in FIG. 11B does not store theregistration data of the called user.

In this embodiment of the present invention, when a P-CSCF with which auser terminal currently registers is faulty, the terminal is finallytriggered, according to a message that carries a redundancy identifier,to re-register with a P-CSCF, and a called service of the user terminalis borne in the re-registered P-CSCF, which avoids problems in the priorart that a dual-host fault is caused because heartbeat detection needsto be performed between a primary network element and a secondarynetwork element and processing is complex because a same IP needs to bepresented to the outside. In addition, fault recovery can be quicklycompleted in an existing network architecture.

Referring to FIG. 12, FIG. 12 is a schematic flowchart of Embodiment 3of an apparatus for recovering a called service of a terminal accordingto the present invention. The apparatus in this embodiment of thepresent invention may be a PCRF. Specifically, the apparatus includes:

a generating module 31, configured to generate a registration triggeringrequest when a reselection request that is sent by a P-CSCF and carriesa P-CSCF re-select flag and a user name is received, where the user nameincludes an identifier of a user terminal corresponding to a calledrequest received by an S-CSCF, that is, an identifier of a user terminalof a called party, and may be specifically an IP address, a user servicepermission, other user configuration information, and the like of theuser terminal used as the called party; and

a sending module 32, configured to send the generated registrationtriggering request to a gateway connected to the user terminal indicatedby the user name, so that the gateway triggers the user terminalindicated by the user name to re-register with a P-CSCF to bear a calledservice of the user terminal.

The reselection request is generated by the P-CSCF according to anotification message that is sent by the S-CSCF and carries the username and a redundancy identifier, where the redundancy identifier isused to instruct to trigger the user terminal indicated by the user nameto re-register with the P-CSCF.

After receiving the reselection request such as the STR that carries theP-CSCF re-select flag, the generating module 31 needs to perform aprocedure of recovering the called service of the user terminalcorresponding to the user name, that is, generating the registrationtriggering request and sending the registration triggering request tothe gateway of the user terminal corresponding to the user name. Thegateway may be a P-GW or an S-GW. The gateway directly triggers the userterminal to reselect a new P-CSCF.

Further, optionally, the generating module 32 is specifically configuredto: when the reselection request that is sent by the P-CSCF and carriesthe P-CSCF re-select flag and the user name is received, generate aregistration triggering request that carries a session release message.

The session release message is used to instruct the gateway connected tothe user terminal indicated by the user name to request a mobilitymanagement entity MME to delete a user bearer of a user terminal.

The registration triggering request may be an RAR that carries aSession-Release-Cause AVP, that is, an attribute field ofSession-Release-Cause and a field value are carried in the RAR toinstruct the gateway to request to delete all bearers of the userterminal. The gateway directly requests to release an IMS PDN of theuser terminal corresponding to the user name.

The user terminal loses a connection after the MME deletes the IMS PDN.The user terminal detects an access failure, and automatically performsa new registration procedure to complete registration with the P-CSCFand the like, to implement network accessing. The user terminal selectsan available third P-CSCF and initiates SIP initial registration withthe third P-CSCF. After receiving a registration request of the user,the third P-CSCF sends a message to an S-CSCF to which the user terminalbelongs, to complete the registration request. The third P-CSCF maydetermine, by using an I-CSCF, the S-CSCF to which the user terminalbelongs, and then send a registration complete message to the foundS-CSCF to which the user terminal belongs, to complete the registrationrequest. Then, the S-CSCF delivers the called request to the thirdP-CSCF to bear the called service.

Alternatively, optionally, the generating module 32 is specificallyconfigured to: when the reselection request that is sent by the P-CSCFand carries the P-CSCF re-select flag and the user name is received,generate a registration triggering request that carries update P-CSCFaddress information.

The update P-CSCF address information is used to instruct the gatewayconnected to the user terminal indicated by the user name to generate alist of available P-CSCF addresses and send the list of the availableP-CSCF addresses to the user terminal indicated by the user name.

The registration triggering request is an RAR that carries an updateP-CSCF address request. After receiving the RAR, the gateway sends anUpdate PDP Context message to the user terminal, so that the userterminal completes re-registration. After receiving the Update PDPContext, the user terminal updates a local P-CSCF list according to thelist of the available P-CSCF addresses in the Update PDP Context, checkswhether an initial P-CSCF with which a local end registers is in thelist, and if not, the user terminal initiates a procedure ofre-registering with a P-CSCF, which may be specifically selecting anavailable third P-CSCF from a new P-CSCF list delivered by the gatewayand registering with the third P-CSCF to bear the called service of theuser terminal. The third P-CSCF may determine, by using an I-CSCF, anS-CSCF to which the user terminal belongs, and then send a registrationcomplete message to the found S-CSCF to which the user terminal belongs,to complete the registration request. Then, the S-CSCF delivers thecalled request to the third P-CSCF to bear the called service.

In this embodiment of the present invention, when a P-CSCF with which auser terminal currently registers is faulty, the terminal is finallytriggered, according to a message that carries a redundancy identifier,to re-register with a P-CSCF, and a called service of the user terminalis borne in the re-registered P-CSCF, which avoids problems in the priorart that a dual-host fault is caused because heartbeat detection needsto be performed between a primary network element and a secondarynetwork element and processing is complex because a same IP needs to bepresented to the outside. In addition, fault recovery can be quicklycompleted in an existing network architecture.

Referring to FIG. 13, FIG. 13 is a schematic flowchart of Embodiment 4of an apparatus for recovering a called service of a terminal accordingto the present invention. The apparatus in this embodiment of thepresent invention may be a P-GW, an S-GW, or another gateway.Specifically, the apparatus includes:

a receiving unit 41, configured to receive a registration triggeringrequest that is sent by a PCRF entity and carries a user name; and

a triggering module 42, configured to trigger a user terminal indicatedby the user name to re-register with a P-CSCF to bear a called serviceof the user terminal.

The registration triggering request is generated when the PCRF receivesa reselection request that is sent by a P-CSCF and carries a P-CSCFre-select flag and the user name, and the reselection request isgenerated by the P-CSCF according to a notification message that is sentby an S-CSCF and carries the user name and a redundancy identifier,where the redundancy identifier is used to instruct to trigger the userterminal indicated by the user name to re-register with the P-CSCF.

Further, optionally, as shown in FIG. 13, the triggering module 42 mayspecifically include:

a first sending unit 421, configured to: when the registrationtriggering request carries a session release message, send, to a MME, arelease request that carries the user name, so that the MME deletes auser bearer of the user terminal indicated by the user name; or

a second sending unit 422, configured to: when the registrationtriggering request carries update P-CSCF address information, acquire alist of available P-CSCF addresses and send the list of the availableP-CSCF addresses to the user terminal indicated by the user name, sothat the user terminal selects a P-CSCF from the list of the availableP-CSCF addresses and registers with the selected P-CSCF.

After a gateway receives an RAR that is sent by the PCRF and carries aSession-Release-Cause AVP, the first sending unit 421 instructs the MMEto delete an IMS PDN of a user, and triggers the user terminal tore-register with a new P-CSCF. However, when the gateway receives an RARthat is sent by the PCRF and carries an update P-CSCF address request,the second sending unit 422 acquires an Update PDP Context message andsends the Update PDP Context message to the user terminal to trigger theuser terminal to update a local P-CSCF list according to the list of theavailable P-CSCF addresses in the Update PDP Context message, and afterdetermining that an updated local P-CSCF list does not include aninitial P-CSCF with which a local end has registered, selects a newP-CSCF and registers with the selected P-CSCF to completere-registration.

In this embodiment of the present invention, when a P-CSCF with which auser terminal currently registers is faulty, the terminal is finallytriggered, according to a message that carries a redundancy identifier,to re-register with a P-CSCF, and a called service of the user terminalis borne in the re-registered P-CSCF, which avoids problems in the priorart that a dual-host fault is caused because heartbeat detection needsto be performed between a primary network element and a secondarynetwork element and processing is complex because a same IP needs to bepresented to the outside. In addition, fault recovery can be quicklycompleted in an existing network architecture.

Referring to FIG. 14, FIG. 14 is a schematic structural diagram ofEmbodiment 5 of an apparatus for recovering a called service of aterminal according to the present invention. The apparatus in thisembodiment of the present invention may be a user terminal that is usedas a called party and is corresponding to a called request.Specifically, the apparatus includes:

a registration initiating module 51, configured to: when an accessfailure is detected, initiate a registration request for registeringwith a P-CSCF, so that a re-registered P-CSCF bears a called servicewhen an initial P-CSCF is faulty; and

a registration selection module 52, configured to: when a list ofavailable P-CSCF addresses that is sent by a gateway is received, selecta P-CSCF from the list of the available P-CSCF addresses and registerwith the selected P-CSCF, so that the re-registered P-CSCF bears thecalled service when the initial P-CSCF is faulty.

The user terminal loses a connection after an MME deletes an IMS PDN.The registration initiating module 51 detects that the access failure,and automatically performs a new registration procedure to completeregistration with the P-CSCF and the like, to implement networkaccessing. The registration initiating module 51 selects an availablethird P-CSCF, and initiates SIP initial registration with the thirdP-CSCF. After receiving a registration request of a user terminal, thethird P-CSCF sends a message to an S-CSCF to which the user terminalbelongs, to complete the registration request. The third P-CSCF maydetermine, by using an I-CSCF, the S-CSCF to which the user terminalbelongs, and then send a registration complete message to the foundS-CSCF to which the user terminal belongs, to complete the registrationrequest. Then, the S-CSCF delivers the called request to the thirdP-CSCF to bear the called service.

Further, optionally, as shown in FIG. 14, the registration selectionmodule 52 may specifically include:

a determining unit, configured to: when the list of the available P-CSCFaddresses that is sent by the gateway is received, determine whether thelist of the available P-CSCF addresses includes a host name of theinitial P-CSCF with which the user terminal currently registers; and

a registration selecting unit, configured to: if the list of theavailable P-CSCF addresses does not include the host name of the initialP-CSCF, select the P-CSCF from the list of the available P-CSCFaddresses and register with the selected P-CSCF.

The registration triggering request is an RAR that carries an updateP-CSCF address request. After receiving the RAR, the gateway sends anUpdate PDP Context message to the user terminal, so that the userterminal completes re-registration. After receiving the Update PDPContext, the registration selection module 52 updates a local P-CSCFlist according to the list of the available P-CSCF addresses in theUpdate PDP Context, checks whether an initial P-CSCF with which a localend registers is in the list, and if not, the user terminal initiates aprocedure of re-registering with a P-CSCF, which may be specificallyselecting the available third P-CSCF3 from a new P-CSCF list deliveredby the gateway and registering with the third P-CSCF3 to bear the calledservice of the user terminal. The third P-CSCF may determine, by usingan I-CSCF, the S-CSCF to which the user terminal belongs, and then senda registration complete message to the found S-CSCF to which the userterminal belongs, to complete the registration request. Then, the S-CSCFdelivers the called request to the third P-CSCF to bear the calledservice.

In this embodiment of the present invention, when a P-CSCF with which auser terminal currently registers is faulty, the terminal canre-register with a new P-CSCF according to a structure, on a networkside, for recovery processing based on a message that carries aredundancy identifier, and carry a called service of the user terminalin the new P-CSCF, which avoids problems in the prior art that adual-host fault is caused because heartbeat detection needs to beperformed between a primary network element and a secondary networkelement and processing is complex because a same IP needs to bepresented to the outside. In addition, fault recovery can be quicklycompleted in an existing network architecture.

Referring to FIG. 15, FIG. 15 is a schematic structural diagram of asystem for recovering a called service of a terminal according to anembodiment of the present invention. The system in this embodiment ofthe present invention may specifically include: a serving-call sessioncontrol function S-CSCF1 entity, at least two proxy-call session controlfunction P-CSCF entities, and a user terminal 4, where the at least twoP-CSCFs include a second P-CSCF3 and a first P-CSCF2 with which the userterminal currently registers.

The S-CSCF is configured to: when a called request of the user terminal4 is received, query the first P-CSCF2 with which the user terminal 4currently registers; and if it is detected that the first P-CSCF2 isfaulty, select the second P-CSCF3, and send, to the second P-CSCF, anotification message that carries a redundancy identifier, where theredundancy identifier is used to instruct the available P-CSCF totrigger the user terminal 4 to re-register with the P-CSCF.

The second P-CSCF3 is configured to trigger the user terminal 4 tore-register with the P-CSCF.

The S-CSCF is further configured to: when a registration completemessage sent by the P-CSCF with which the user terminal 4 re-registersis received, deliver the called request to the re-registered P-CSCF tobear a called service of the user terminal 4.

The second P-CSCF specifically triggers, by using a policy and chargingrules function PCRF entity, the user terminal to re-register with theP-CSCF.

Further, optionally, as shown in FIG. 15, the system further includes aDNS server 5.

The S-CSCF is further configured to configure, on the DNS server 5, afirst identifier and a second identifier according to a host name of thefirst P-CSCF2, where the first identifier includes an IP address of thefirst P-CSCF2, and the second identifier includes an IP address of thesecond P-CSCF3.

Further, optionally, as shown in FIG. 15, the system may further includea PCRF entity 6.

The second P-CSCF3 is specifically configured to: generate, according tothe notification message that is sent by the S-CSCF and carries a username and the redundancy identifier, a reselection request that carries aP-CSCF re-select flag and the user name, and send the reselectionrequest to the PCRF6.

The PCRF6 is configured to instruct, according to the P-CSCF re-selectflag, the user terminal 4 indicated by the user name to reselect aP-CSCF to bear the called service of the user terminal 4.

Further, optionally, as shown in FIG. 15, the system may further includea Diameter routing agent DRA7.

The DRA7 is configured to: receive the reselection request sent by thesecond P-CSCF3, and send the reselection request to the PCRF6.

Further, optionally, as shown in FIG. 15, the system may further includea gateway 8 connected to the user terminal 4.

The PCRF6 is specifically configured to: generate a registrationtriggering request when the reselection request that is sent by theP-CSCF and carries the P-CSCF re-select flag and the user name isreceived, and send the registration triggering request to the gateway 8.

The gateway 8 is configured to trigger, according to the registrationtriggering request, the user terminal 4 indicated by the user name tore-register with the P-CSCF to bear the called service of the userterminal 4.

Further, the gateway 8 is specifically configured to: when theregistration triggering request carries a session release message, send,to an MME, a release request that carries the user name, so that the MMEdeletes a user bearer of the user terminal 4 indicated by the user name;or

when the registration triggering request carries update P-CSCF addressinformation, acquire a list of available P-CSCF addresses and send thelist of the available P-CSCF addresses to the user terminal 4 indicatedby the user name, so that the user terminal 4 selects a P-CSCF from thelist of the available P-CSCF addresses and registers with the selectedP-CSCF.

Further, the user terminal 4 is further configured to: when an accessfailure is detected, initiate a registration request for registeringwith a P-CSCF, so that a re-registered P-CSCF bears the called servicewhen the initial P-CSCF is faulty; or when the list of the availableP-CSCF addresses that is sent by the gateway 8 is received, select aP-CSCF from the list of the available P-CSCF addresses, and registerwith the selected P-CSCF, so that the re-registered P-CSCF bears thecalled service when the initial P-CSCF is faulty.

Specifically, for specific implementation of the foregoing user terminal4, refer to descriptions of the user terminal that is used as the calledparty and is corresponding to the called request in the foregoing methodembodiments and apparatus embodiments; for specific implementation ofthe foregoing S-CSCF1, refer to descriptions of the S-CSCF in theforegoing method embodiments and apparatus embodiments; for specificimplementation of the foregoing first P-CSCF2 and the foregoing secondP-CSCF3, refer to descriptions of the faulty P-CSCF and the availableP-CSCF in the foregoing method embodiments and apparatus embodiments;for specific implementation of the foregoing PCRF6, refer todescriptions of the PCRF in the foregoing method embodiments andapparatus embodiments; the foregoing gateway 8 may be an S-GW or a P-GW,and refer to descriptions of the gateway in the foregoing methodembodiments and apparatus embodiments. Details are not described herein.

In this embodiment of the present invention, when a P-CSCF with which auser terminal currently registers is faulty, the terminal is finallytriggered, according to a message that carries a redundancy identifier,to re-register with a P-CSCF, and a called service of the user terminalis borne in the re-registered P-CSCF, which avoids problems in the priorart that a dual-host fault is caused because heartbeat detection needsto be performed between a primary network element and a secondarynetwork element and processing is complex because a same IP needs to bepresented to the outside. In addition, fault recovery can be quicklycompleted in an existing network architecture.

Specifically, an embodiment of the present invention further provides anetwork device. Referring to a schematic structural diagram of thenetwork device as shown in FIG. 16, the network device may bespecifically an S-CSCF or an IBCF, and may include a receiving apparatus1200, a processor 1100, and a sending apparatus 1300, where theprocessor 1100 is configured to perform:

when the receiving apparatus 1200 receives a called request of a userterminal, querying an initial P-CSCF entity with which the user terminalcurrently registers; and

if it is detected that the initial P-CSCF is faulty, selecting anavailable P-CSCF and sending a notification message to the availableP-CSCF by using the sending apparatus 1300, to trigger the user terminalto re-register with the P-CSCF.

In a possible implementation manner, the processor 1100 may beconfigured to: after selecting the available P-CSCF, send, to theavailable P-CSCF by using the sending apparatus 1300, a notificationmessage that carries a redundancy identifier, where the redundancyidentifier is used to instruct the available P-SCCF to trigger the userterminal to re-register with the P-CSCF. In another possibleimplementation manner, the processor 1100 may be configured to: afterselecting the available P-CSCF, send the called request of the userterminal to the available P-CSCF by using the sending apparatus 1300, soas to trigger, when the available P-CSCF determines that no registrationdata of a called user is stored, the user terminal to re-initiate IMSregistration.

The processor 1100 may further be configured to: when the receivingapparatus 1200 receives a registration complete message sent by theP-CSCF with which the user terminal re-registers, deliver the calledrequest to the re-registered P-CSCF by using the sending apparatus 1300,to bear a called service of the user terminal.

The available P-CSCF specifically triggers, by using a PCRF, the userterminal to re-register with the P-CSCF.

Further, optionally, before performing the selecting an available P-CSCFand sending a notification message to the available P-CSCF, if it isdetected that the initial P-CSCF is faulty, the processor 1100 isfurther configured to perform:

configuring a first identifier and a second identifier for the initialP-CSCF, where the first identifier includes an IP address of the initialP-CSCF, and the second identifier includes an IP address of a P-CSCFexcept the initial P-CSCF.

Further, optionally, when performing the configuring a first identifierand a second identifier for the initial P-CSCF, the processor 1100 isspecifically configured to perform:

configuring, on a domain name system DNS server, the first identifierand the second identifier according to a host name of the initialP-CSCF.

Further, optionally, when performing the selecting an available P-CSCFand sending a notification message to the available P-CSCF, if it isdetected that the initial P-CSCF is faulty, the processor 1100 isspecifically configured to perform:

acquiring the first identifier and the second identifier that areconfigured for the initial P-CSCF;

if it is detected, according to the acquired first identifier, that theinitial P-CSCF corresponding to the first identifier is faulty, using aP-CSCF corresponding to the second identifier as the available P-CSCF;and

sending the notification message to the available P-CSCF according tothe second identifier.

Further, optionally, when performing the delivering the called requestto the re-registered P-CSCF to the called service of the user terminal,the processor 1100 is configured to send the called request to there-registered P-CSCF, so that the re-registered P-CSCF sends the calledrequest to the user terminal to perform the called service.

In this embodiment of the present invention, after a called request isreceived, if it is detected that a P-CSCF with which a user terminalthat is used as a called party and is corresponding to the calledrequest currently registers is faulty, a corresponding message thatcarries a redundancy identifier is generated to finally trigger theterminal to re-register with a P-CSCF, and a called service of the userterminal is borne in the re-registered P-CSCF, which avoids problems inthe prior art that a dual-host fault is caused because heartbeatdetection needs to be performed between a primary network element and asecondary network element and processing is complex because a same IPneeds to be presented to the outside. In addition, fault recovery can bequickly completed in an existing network architecture.

Specifically, an embodiment of the present invention further providesanother network device. Referring to a schematic structural diagram ofthe another network device shown in FIG. 17A, the network device may bespecifically a P-CSCF, and may include a receiving apparatus 2200, aprocessor 2100, and a sending apparatus 2300, where the processor 2100is configured to perform:

receiving, by using the receiving apparatus 2200, a notification messagethat is sent by a S-CSCF entity and carries a user name;

generating, if it is found, by means of parsing, that the notificationmessage further includes a redundancy identifier, a reselection requestthat carries a P-CSCF re-select flag and the user name; and

sending, by using the sending apparatus 2300, the reselection request toa PCRF entity that manages a user terminal indicated by the user name,so that the PCRF instructs, according to the P-CSCF re-select flag, theuser terminal indicated by the user name to reselect a P-CSCF to bear acalled service of the user terminal.

The notification message that carries the redundancy identifier isgenerated by the S-CSCF when a P-CSCF with which the user terminalcorresponding to a received called request registers is faulty, and theredundancy identifier is used to instruct to trigger the user terminalto re-register with a P-CSCF.

Further, optionally, when performing the sending the reselection requestto a policy and charging rules function PCRF entity that manages a userterminal indicated by the user name, the processor 2100 is configured toperform:

sending the reselection request to a DRA, so that the DRA sends,according to the user name in the reselection request, the reselectionrequest to the PCRF that manages the user terminal indicated by the username.

Further, optionally, before performing the generating, if it is found,by means of parsing, that the notification message further includes aredundancy identifier, a reselection request that carries a P-CSCFre-select flag and the user name, the processor 2100 is furtherconfigured to perform:

determining whether the user terminal indicated by the user nameregisters with a local end; and

if the user terminal does not register with the local end, performingthe generating, if it is found, by means of parsing, that thenotification message further includes a redundancy identifier, areselection request that carries a P-CSCF re-select flag and the username.

Further, optionally, the processor 2100 is further configured toperform:

when a registration request of the user terminal is received, sending aregistration complete message to an S-CSCF to which the user terminalbelongs, to complete registration of the user terminal.

In this embodiment of the present invention, when a P-CSCF with which auser terminal currently registers is faulty, the terminal is finallytriggered, according to a message that carries a redundancy identifier,to re-register with a P-CSCF, and a called service of the user terminalis borne in the re-registered P-CSCF, which avoids problems in the priorart that a dual-host fault is caused because heartbeat detection needsto be performed between a primary network element and a secondarynetwork element and processing is complex because a same IP needs to bepresented to the outside. In addition, fault recovery can be quicklycompleted in an existing network architecture.

Embodiments of the present invention further provide an apparatus forrecovering a called service of a terminal, as shown in FIG. 17B. Theapparatus shown in FIG. 17B may be a P-CSCF. The apparatus includes areceiving apparatus 2200′, a processor 2100′, and a sending apparatus2300′, where the processor 2100′ is configured to perform:

receiving a called request of a user terminal by using the receivingapparatus 2200′;

determining that no registration data of a called user is stored; and

sending, to a PCRF that manages the user terminal and by using thesending apparatus 2300′, a request for triggering the user terminal tore-initiate IMS registration.

The processor 2100′ receives, by using the receiving apparatus 2200′, acalled request of the user terminal that is sent by an S-CSCF or anIBCF.

Optionally, the processor 2100′ may be configured to send, to the PCRFby using the sending apparatus 2300′, a request that carries are-registration identifier, where the re-registration identifier is usedto trigger the user terminal to re-initiate the IMS registration. In apossible implementation manner, the request that carries there-registration identifier may be an STR or an AAR.

Optionally, when determining that no registration data of a called useris stored, the processor 2100′ is configured to determine that theapparatus shown in FIG. 17B does not store the registration data of thecalled user.

Specifically, an embodiment of the present invention further providesstill another network device. Referring to a schematic structuraldiagram of the still another network device shown in FIG. 18, thenetwork device may be specifically a PCRF, and may include a receivingapparatus 3200, a processor 3100, and a sending apparatus 3300, wherethe processor 3100 is configured to perform:

generating a registration triggering request when the receivingapparatus 3200 receives a reselection request that is sent by a P-CSCFand carries a P-CSCF re-select flag and a user name; and

sending, by using the sending apparatus 3300, the generated registrationtriggering request to a gateway connected to a user terminal indicatedby the user name, so that the gateway triggers the user terminalindicated by the user name to re-register with a P-CSCF to bear a calledservice of the user terminal.

The reselection request is generated by the P-CSCF according to anotification message that is sent by an S-CSCF and carries the user nameand a redundancy identifier, where the redundancy identifier is used toinstruct to trigger the user terminal indicated by the user name tore-register with the P-CSCF.

Further, optionally, when performing the generating a registrationtriggering request when a reselection request that is sent by a P-CSCFand carries a P-CSCF re-select flag and a user name is received, theprocessor 3100 is specifically configured to perform:

when the reselection request that is sent by the P-CSCF and carries theP-CSCF re-select flag and the user name is received, generating aregistration triggering request that carries a session release message,where

the session release message is used to instruct the gateway connected tothe user terminal indicated by the user name to request an MME to deletea user bearer of a user terminal.

Further, optionally, when performing the generating a registrationtriggering request when a reselection request that is sent by a P-CSCFand carries a P-CSCF re-select flag and a user name is received, theprocessor 3100 is specifically configured to perform:

when the reselection request that is sent by the P-CSCF and carries theP-CSCF re-select flag and the user name is received, generating aregistration triggering request that carries update P-CSCF addressinformation, where

the update P-CSCF address information is used to instruct the gatewayconnected to the user terminal indicated by the user name to generate alist of available P-CSCF addresses and send the list of the availableP-CSCF addresses to the user terminal indicated by the user name.

In this embodiment of the present invention, when a P-CSCF with which auser terminal currently registers is faulty, the terminal is finallytriggered, according to a message that carries a redundancy identifier,to re-register with a P-CSCF, and a called service of the user terminalis borne in the re-registered P-CSCF, which avoids problems in the priorart that a dual-host fault is caused because heartbeat detection needsto be performed between a primary network element and a secondarynetwork element and processing is complex because a same IP needs to bepresented to the outside. In addition, fault recovery can be quicklycompleted in an existing network architecture.

Specifically, an embodiment of the present invention further providesyet another network device. Referring to a schematic structural diagramof the still another network device shown in FIG. 19, the network devicemay be specifically an S-GW or a P-GW, and may include a receivingapparatus 4200, a processor 4100, and a sending apparatus 4300, wherethe processor 4100 is configured to perform:

when the receiving apparatus 4200 receives a registration triggeringrequest that is sent by a PCRF entity and carries a user name,triggering a user terminal indicated by the user name to re-registerwith a P-CSCF to bear a called service of the user terminal, where

the registration triggering request is generated when the PCRF receivesa reselection request that is sent by a P-CSCF and carries a P-CSCFre-select flag and the user name, and the reselection request isgenerated by the P-CSCF according to a notification message that is sentby an S-CSCF and carries the user name and a redundancy identifier,where the redundancy identifier is used to instruct to trigger the userterminal indicated by the user name to re-register with the P-CSCF.

Further, optionally, when performing the triggering a user terminalindicated by the user name to re-register with a P-CSCF, the processor4100 is configured to perform:

when the registration triggering request carries a session releasemessage, sending, to an MME, a release request that carries the username, so that the MME deletes a user bearer of the user terminalindicated by the user name; or

when the registration triggering request carries update P-CSCF addressinformation, acquiring a list of available P-CSCF addresses and sendingthe list of the available P-CSCF addresses to the user terminalindicated by the user name, so that the user terminal selects a P-CSCFfrom the list of the available P-CSCF addresses and registers with theselected P-CSCF.

In this embodiment of the present invention, when a P-CSCF with which auser terminal currently registers is faulty, the terminal is finallytriggered, according to a message that carries a redundancy identifier,to re-register with a P-CSCF, and a called service of the user terminalis borne in the re-registered P-CSCF, which avoids problems in the priorart that a dual-host fault is caused because heartbeat detection needsto be performed between a primary network element and a secondarynetwork element and processing is complex because a same IP needs to bepresented to the outside. In addition, fault recovery can be quicklycompleted in an existing network architecture.

Specifically, an embodiment of the present invention further providesuser equipment. Referring to a schematic structural diagram of the userequipment shown in FIG. 20, the user equipment includes a receivingapparatus 5200, a processor 5100, and a sending apparatus 5300, wherethe processor 5100 is configured to perform:

when detecting that an access failure, initiating, by using the sendingapparatus 5300, a registration request for registering with a P-CSCF, sothat a re-registered P-CSCF bears a called service when an initialP-CSCF is faulty; and

when the receiving apparatus 5200 receives a list of available P-CSCFaddresses that is sent by a gateway, selecting a P-CSCF from the list ofthe available P-CSCF addresses and registering with the selected P-CSCF,so that the re-registered P-CSCF bears the called service when theinitial P-CSCF is faulty.

Further, optionally, when performing the selecting a P-CSCF from thelist of the available P-CSCF addresses and registering with the selectedP-CSCF, when a list of available P-CSCF addresses that is sent by agateway is received, the processor 5100 is specifically configured toperform:

when the list of the available P-CSCF addresses that is sent by thegateway is received, determining whether the list of the availableP-CSCF addresses includes a host name of the initial P-CSCF with which auser terminal currently registers; and

if the list of the available P-CSCF addresses does not include the hostname of the initial P-CSCF, selecting the P-CSCF from the list of theavailable P-CSCF addresses and registering with the selected P-CSCF.

In this embodiment of the present invention, when a P-CSCF with which auser terminal currently registers is faulty, the terminal canre-register with a new P-CSCF according to a structure, on a networkside, for recovery processing based on a message that carries aredundancy identifier, and carry a called service of the user terminalin the new P-CSCF, which avoids problems in the prior art that adual-host fault is caused because heartbeat detection needs to beperformed between a primary network element and a secondary networkelement and processing is complex because a same IP needs to bepresented to the outside. In addition, fault recovery can be quicklycompleted in an existing network architecture.

A person of ordinary skill in the art may understand that all or some ofthe processes of the methods in the embodiments may be implemented by acomputer program instructing relevant hardware. The program may bestored in a computer readable storage medium. When the program runs, theprocesses of the methods in the embodiments are performed. The foregoingstorage medium may include: a magnetic disk, an optical disc, aread-only memory (ROM), or a random access memory (RAM).

What is disclosed above is merely exemplary embodiments of the presentinvention, and certainly is not intended to limit the protection scopeof the present invention. Therefore, equivalent variations made inaccordance with the claims of the present invention shall fall withinthe scope of the present invention.

What is claimed is:
 1. A method for recovering a called service of aterminal performed by a Serving Call Session Control Function (S-CSCF),the method comprising: receiving a called request of the user terminal;querying an initial proxy-call session control function (P-CSCF) entitywith which the user terminal currently registers; detecting that theinitial P-CSCF is faulty; selecting an available P-CSCF; notifying theavailable P-CSCF to trigger the user terminal to re-initiate IPMultimedia Subsystem (IMS) registration, wherein the available P-CSCFtriggers, by using a policy and charging rules function (PCRF) entity,the user terminal to re-initiate IMS registration; and delivering thecalled request to a re-registered P-CSCF to bear the called service ofthe user terminal after the user terminal completes the IMSregistration.
 2. The method according to claim 1, wherein notifying theavailable P-CSCF to trigger the user terminal to re-initiate IMSregistration comprises: sending, to the available P-CSCF, a notificationmessage that carries a redundancy identifier, wherein the redundancyidentifier is used to instruct the available P-CSCF to trigger the userterminal to re-initiate the IMS registration.
 3. The method according toclaim 1, wherein notifying the available P-CSCF to trigger the userterminal to re-initiate IMS registration comprises: sending the calledrequest of the user terminal to the available P-CSCF; and when theavailable P-CSCF determines that no registration data of a called useris stored, triggering the user terminal to re-initiate the IMSregistration.
 4. The method according to claim 1, wherein before theselecting an available P-CSCF, the method further comprises: configuringa first identifier and a second identifier for the initial P-CSCF,wherein the first identifier comprises an internet protocol (IP) addressof the initial P-CSCF, and the second identifier comprises an IP addressof a P-CSCF except the initial P-CSCF.
 5. The method according to claim4, wherein configuring the first identifier and the second identifierfor the initial P-CSCF comprises: configuring, on a domain name system(DNS) server, the first identifier and the second identifier accordingto a host name of the initial P-CSCF.
 6. The method according to claim4, wherein selecting the available P-CSCF and notifying the availableP-CSCF, if it is detected that the initial P-CSCF is faulty comprises:acquiring the first identifier and the second identifier that areconfigured for the initial P-CSCF; if it is detected, according to theacquired first identifier, that the initial P-CSCF corresponding to thefirst identifier is faulty, using a P-CSCF corresponding to the secondidentifier as the available P-CSCF; and sending a notification messageto the available P-CSCF according to the second identifier.
 7. Themethod according to claim 1, wherein delivering the called request tothe re-registered P-CSCF to bear the called service of the user terminalcomprises: sending the called request to the re-registered P-CSCF, sothat the re-registered P-CSCF sends the called request to the userterminal to perform the called service.
 8. An apparatus for recovering acalled service of a terminal, comprising a processor and anon-transitory computer readable medium containing computer executableinstructions stored thereon, such that when the processor executes theinstructions, the processor is configured to: receive a called requestof the user terminal; query an initial proxy-call session controlfunction (P-CSCF) entity with which the user terminal currentlyregisters; detect that the initial P-CSCF is faulty; select an availableP-CSCF and notify the available P-CSCF to trigger the user terminal tore-initiate IP Multimedia Subsystem (IMS) registration, wherein theavailable P-CSCF triggers, by using a policy and charging rules function(PCRF) entity, the user terminal to re-initiate IMS registration; anddeliver the called request to a re-registered P-CSCF to bear the calledservice of the user terminal after the user terminal completes the IMSregistration.
 9. The apparatus according to claim 8, wherein theprocessor is further configured to: after selecting the availableP-CSCF, send, to the available P-CSCF, a notification message thatcarries a redundancy identifier, wherein the redundancy identifier isused to instruct the available P-CSCF to trigger the user terminal tore-initiate the IMS registration.
 10. The apparatus according to claim8, wherein the processor is further configured to: after selecting theavailable P-CSCF, send the called request of the user terminal to theavailable P-CSCF, so as to trigger, when the available P-CSCF determinesthat no registration data of a called user is stored, the user terminalto re-initiate the IMS registration.
 11. The apparatus according toclaim 8, wherein the processor is further configured to: configure afirst identifier and a second identifier for the initial P-CSCF, whereinthe first identifier comprises an internet protocol (IP) address of theinitial P-CSCF, and the second identifier comprises an IP address of aP-CSCF except the initial P-CSCF.
 12. The apparatus according to claim11, wherein the processor is further configured to: configure, on adomain name system (DNS) server, the first identifier and the secondidentifier according to a host name of the initial P-CSCF.
 13. Theapparatus according to claim 11, wherein the processor is furtherconfigured to: acquire the first identifier and the second identifierthat are configured for the initial P-CSCF; if, according to theacquired first identifier, the initial P-CSCF corresponding to the firstidentifier is faulty, use a P-CSCF corresponding to the secondidentifier as the available P-CSCF; and send a notification message tothe available P-CSCF according to the second identifier.
 14. Theapparatus according to claim 8, wherein the processor is furtherconfigured to: send the called request to the re-registered P-CSCF, sothat the re-registered P-CSCF sends the called request to the userterminal to perform the called service.